Colt SP 1 electropencil markings, trying to figure out meaning
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Thread: Colt SP 1 electropencil markings, trying to figure out meaning

  1. #1
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    Default Colt SP 1 electropencil markings, trying to figure out meaning

    Bit of history, picked up a 1970's Colt SP1 back in April and have been trying to figure out more about it. Rifle has absolutely been carried around a lot, the furniture has lots of light scratches and wear marks, but no rust. Rifle has a lot of older M16 style GI parts that are probably original but I'm not a 100% certain. Three prong flash hider, teardrop assist, old style rear sight, triangular handguard, 1/12 twist pencil .556 barrel etc. The gunstore claimed they were 3rd party and surplus parts added on when I was looking at it but if so they've been on there a very long time. At the time, I mainly bought it because the price seemed good and it was the exact make I wanted in a retro AR. Resell or collectors value didn't concern me as I planned on shooting it, and everything as far as a shooter was concerned was in great condition (bore, trigger, strong rifling, very smooth action, etc.)

    While looking over the rifle I found an electropenciled serial number starting with T.D.C. and am starting to wonder if this rifle was used by the Tennessee Department of Corrections or something else with that abbreviation. The rifle still has it's original serial number stamped in by colt beneath it in the 74XXX range. I live in southern KY so it would make sense that it was a surplused rifle from TN. It would also explain the clear carrying wear but very little evidence of actually being fired.

    My main questions are

    *Anyone have an ideas on what T.D.C could be aside from TN Dept of Corrections?
    *Are these original parts from colt or just random surplus pieces thrown on?


    Has anyone ever seen an SP1 with markings like this? The T.D.C. number and Sp1 serial number appear to have no relation that I can tell. I've debated getting one of those certificates from colt, but not sure if it would really answer the questions I have. If you've tried that before I'd appreciate your thoughts on if it was worth your time or not. My best guess is it was a TN dept of Corrections rifle used for guarding a prison or something. I'm expecting it to be a fairly boring origin but it's always cool to learn more about a rifle's history.

    Hopefully you guys found this interesting and any help or advice is appreciated. Thanks
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  2. #2
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    judging by the front pin, you have a Nodak Spud M16 A1 upper on a Colt Commercial SP1 made in 1977

    would need to see pics of the internals to be exact, but betting it may have a M16 hammer, and possible a M16 carrier
    what's so funny about peace love and understanding?

  3. #3
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    judging by the front pin, you have a Nodak Spud M16 A1 upper on a Colt Commercial SP1 made in 1977

    would need to see pics of the internals to be exact, but betting it may have a M16 hammer, and possible a M16 carrier
    what's so funny about peace love and understanding?

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  5. #4
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    In the 60’s, 70’s and up into the 80’s it wasn’t uncommon for local police to suggest gun owners engrave their social security number into a firearm. My guess would be the TDC is the guy’s initials and rest is his SS number.
    When your smiling the whole world smiles with you

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    Depending on the number of digits, it could be TDC's date of birth. My Dad marked a couple of firearms with my info when he gave them to me in the early 70's.
    Doug

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  7. #6
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    could be ticondaroga dairy consortium too- There is really no way to know what it stands for or the number ( we can't see the number of digits to know that) unless you have some fairly solid written background, it will never matter and is just conjecture. But as noted above the upper would not apparently be COLT SP1 with the Offset pin without close up detailed pics to evaluate the parts ( looking at the over all it is probably an M16 upper) Enjoy the rifle for what it is - a great shooter.

  8. #7
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    Here's a picture of the hammer itself if that's what you were wanting to see. It is marked with two colt stole C's, one has a triangle inside it and the other is a C with two circles around it. Only marking I could find on the carrier was JC. The upper is marked "NDS" just under the windage adjustment.

    The TDC number is 5 digits as 79XXX. Doesn't appear to be a social or birth date. Not too worried about it either way, just hoped someone would say something like "oh yeah I've seen one like that before."

    As for the parts not being original that would match up with the stores appraisal then. Someone must have taken the time back in the day to source other parts to make a reproduction of an A1. Makes me feel better about shooting it, so that's a bit of a relief. It's a great shooter so I'm happy either way. Thanks guys, appreciate it
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  9. #8
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    first off, welcome to the board

    upper receiver is definitely a "retro" NODAK SPUD, lower is a colt SP1. bolt carrier is commercially made by J.C. Machine. what you have is AR15A1 assembled from pieces and parts. shoot and enjoy
    Last edited by SfcRet; 06-25-2020 at 08:10 PM.

  10. #9
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    you could always contact Colt and see if they can letter the gun,


    cost is $100 for an AR,,
    what's so funny about peace love and understanding?

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    Quote Originally Posted by Lyman1903 View Post
    you could always contact Colt and see if they can letter the gun,


    cost is $100 for an AR,,
    why should he spend a 100 bucks to "letter the gun"? it's not in the original configuration that it came from the factory, so there is zero collector value to that rifle. the value is the sum of the parts.

  12. #11
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    Welcome to the retro AR world. Sounds like you have a parts gun. Nothing wrong with that, they are fun shooters.

    What are the markings on the barrel up between the flash hider and front sight?

    Retro ARs are big now with many people assembling them out of assorted parts, from NOS, used original to reproductions of various accuracy and quality.

    I current;y have 3 reproductions.

    1. AR15/SP1 with original upper/barrel assembly and original stocks. Reproduction chrome bolt and carrier, FCG and NoDak/Brownells lower.

    2: M16A1 with original barreled upper, stocks. Again with NDS/Brownells lower

    3: M16A2 with Palmetto US Property M16A2 reciever, and a total mismash of parts. Does have a nice heavt barrel though.


    State and local law enforcement agencies back in the '70s generally ordered M16 select fire rifles from Colt, and not semi auto.

    I wouldn't waste the money for a Colt letter an a parts rifle.
    "Is there something up your butt? 'Cause that's dirty and now I gotta touch it."


    "By now the fighting will be close at hand. There's a gun and ammunition, tucked in by the doorway, use it only in emergency". Looks like those days have arrived.

  13. #12
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    Quote Originally Posted by SfcRet View Post
    why should he spend a 100 bucks to "letter the gun"? it's not in the original configuration that it came from the factory, so there is zero collector value to that rifle. the value is the sum of the parts.
    his choice,


    not yours or mine
    what's so funny about peace love and understanding?

  14. #13
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    TDC on a AR15 means Texas Department of Corrections. Your lower may also have a bar code sticker on it. Century procured about 20 of these and sold them in 2015.

  15. #14
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    Give her a go at the range and let us know how she shoots. Nothing wrong with a mutt; I have a couple that shoot very well.
    Interested in buying a factory original Izhevsk PU sniper with original wartime matched scope. Long shot but a guy can dream!

  16. #15
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    Thanks Hal, there's no marks on the barrel between the front sight and flash hider. The barrel was marked near the receiver with the Colt C "NATO .556 1/12" so it appears to be original barrel. I'd take it off to show you but it's a two man job to get the handguard off, the ring is very stiff. Had a gunsmith check it out and he needed a second set of hands too.

    It shoots great. I had never shot an AR before, up till now I had mostly done handguns and old military bolt actions with the odd 20 gauge. It was pretty funny first time I took it to the range. I had a target out at maybe 50 yards trying to figure out where to hold while everyone else was set up half that range with new AR's. One guy asked me "how the heck can you hit anything at that range with those sights?" To which I thought "this is nothing, you should try a mosin" but thought better of it and just said I had a lot of practice. Nice guy though, just funny to hear. Felt a little stupid when I realized I was surrounded by $500 AR's when I'd spent double that for a rifle 43 years old, but it ran great and was accurate. I'm sure I overpaid a bit but I was lazy and it was the build I wanted, couldn't resist.

    @Eli, no barcode sticker that I could find. Only "evidence" if you can call it that is a lot of carry wear with little in the way of shooting wear. Knowing it's a parts gun I'm probably not going to bother with the letter unless I just have a $100 with nothing better to do. At that point all the letter is good for is learning who the first place to buy it was. Maybe one day. Right now the priority is just finding ammo, as a new ar15 owner I had just started building a stash when the covid stuff hit, just didn't have enough time to buy more than a few hundred rounds sadly. I've snagged a bit here and there since but it'll probably be a while before I can do a nice long range day again.

  17. #16
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    Quote Originally Posted by MrMoustaffa View Post
    it's a two man job to get the handguard off, the ring is very stiff.
    there is a special tool for taking the handguard off, I'm really surprised your gunsmith didn't have one


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    it would be a real bummer if while using that tool it broke off part of your magwell. wonder if it ever happened?

  19. #18
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    Quote Originally Posted by gramps51 View Post
    it would be a real bummer if while using that tool it broke off part of your magwell. wonder if it ever happened?
    if it takes that much effort, you are either doing it wrong, or got other issues
    what's so funny about peace love and understanding?

  20. #19
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    Quote Originally Posted by gramps51 View Post
    it would be a real bummer if while using that tool it broke off part of your magwell. wonder if it ever happened?
    if your lower was made from GRAHAM CRACKER, that that could happen

  21. #20
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    Seen some cracks in the mag.webs on two..not same brand..nor do I remember much...
    except..one had black grease pushed into it..black marker touch up Bright spots..

    more ars put together unknowingly or like me tried to use my experts here, magazine, Internet ..
    only could trust my judgment in best quality Suggested ..
    basically because I knew nothing about them till mid 2,000..
    first buy Bushmaster org. Varmiter 24 inch barrel..I put a German 3.5 x 15 x 56...
    Fit It..200 yards..it’s better than my spotting scope..Viewing targets..
    (Scope never fit my bolt action rifles with highest rings..Touching the bolt stems..rear bell.)
    only owning sp1..colt.. I didn’t understand a need for the military virson..few came later..Have 7#.
    “Grace+constitutional solvently strength, resistances to Chaos!”

  22. #21
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    My AR-18 has an electro-pen marking on it. I was told it was a police evidence indicator number. It was easier fo the police to assign a number to the gun than try to keep track of it my serial number. The story as told to me, was the gun was owned by a fellow who passed away. His wife didn't want the guns in the house and called the police to remove them, which they did. The executor of his estate decided to let the police hold the guns till he could sell them. I guess some deal was made between the executor of his estate and the police so when the gun was sold, it could be give back to the executor for the sale.
    Bill


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