M48 All milled parts
M48A stamped floor plate only
M48B Receiver ring is still stamped M48A- stamped floor plate, trigger guard mag well is a stamped and welded assy. Also stamped and welded barrel bands and stamped follower.
M48bo Rifle is devoid of manufacture or national markings, no crest noly serial number and proof marks as a rule. Configured either as an M48 or M48B. To date, I have been unable to confirm an M48A configured M48bo.
Prices for excellent examples can go as high as $250 at auction, more off the shelf if you can find one, these days.
I hope this helps.
"In times of trouble and of war, God and soldiers we adore; When wars are done and wrongs are righted, God's forgotten and the soldier slighted." Ye Olde English proverb; origin unknown
I make reproduction Yugoslav pre-WWII rifle slings and bayonet frogs.