Ok, Serial numbers are a mess. Whoever stamped these had no clue about our Arabic numbers.
Rifle is serial number 15566. The parts that match are stamped 366, and th parts that have 366 stamped on them in Arabic numerals, have 566 stamped in Siamese numerals.
The extractor is another example, as it is stamped 820, but the Siamese numbers are 782.
Using Siamese numers:
Bolt and Extractor are 782.
Firing Pin and Cocking Piece are 715
Dust cover is 573
Mag and follower are 486
Handguard is 344, and stock is 366 with only Arabic numerals.
I feel like an Egyption Archeologist :D
I attached the "Rosetta Stone" that I took from the Milsurps site.