ray ----- If you would like I could field strip my carbine and take pics of some internal parts. Are there any particular parts you might care to see ?? Let me know.
I appreciate your new-found interest in this M1 carbine, which as I said before, looks completely consistent with original, as-issued configuration. That could be even further confirmed by looking at markings on other internal components; Standard Products (a Division of General Motors) usually marked all their parts with an "S" where possible. All carbine manufacturers had their own specific code, used primarily for quality control purposes; so, if a particular part were found to be consistently failing, the Ordnance Dept could go back to the manufacturer and perhaps discover defects in metallurgy, machining, heat-treating, etc. The trigger housing (your photo looks like the late stamped/brazed Type 4 = consistent with late production) and should have letters like "ST" or "BE-B" (which is actually an IBM part supplied through lateral support). The hammer should have a letter "S" in it, like "SW", "SS", "SHTE" (letters stacked upon each other) on the left side; the bolt lug (usually the right side) should have an "S" and probably a number following; and the sear will also have the letter "S" in the marking (if visible). The magazine catch should have the marking "SW" on the side facing forward against the magazine. The slide should have the big, loopy "S" on the inside, usually followed by a number. The left side of the rear flip sight should have a small letter "s", indicating "small" side going into the tapered dovetail on the receiver. And the front sight should have the letter "N' behind the blade (Niedner Rifle Company - made sights for many of the carbine manufacturers) in it, either alone or "SN".
Standard Products did not make their own barrels, so your Underwood barrel dated 12-43 is consistent with your late receiver serial number 2132143 indicating late January-early February production timeframe according to Ruth and Duff's book "The M1 Carbine Owner's Guide". The size and placement of the Ordnance Dept acceptance stamp ("Crossed Cannons") on the right side of the buttstock is correct for Standard Products, and an even better confirmation will be found in the slingwell cutout on the left side, which should have "S-HB" (the HB indicated that the stock was made by Hillerich and Bradsby, the maker of the famous Louisville Slugger baseball bats). More rarely, you might find the letters "SJ" - the "J" indicating manufacture by Jamestown Lounge Company in New York. The flat part of the underside of the handguard should also show "S-HB" or "SJ". The magazine marked "AI" is by "Autoyre" for Inland. The big, loopy "S" marking on the sling is not documented anywhere I can find, but could conceivably be in line with the "S" markings for almost every carbine part made by Standard Products - you could tell people that, and nobody could dispute you!
All these markings merely indicate what was most likely on the gun when it was originally issued, and any deviations from that are nothing to apologize for - your carbine looks like a truly excellent example from Standard Products, a relatively rare producer which made less than 3% of all M1 carbines. As for value, you can watch Gunbroker auctions and compare yours to whatever is offered. Hint: although I already have three Standard Products carbines, I would offer you $2,000 for it right now! (But really - don't sell it; keep it as a 40-year family heirloom!)
