I wrote this yesterday, so it's mostly a of ditto Kevin's post.
M15A1-2246 would have been made by Autocar in Feb 1944, the last month of production. ( The last M15A1 would have been Ord S/N 2333.) USA 40150963 is an exact mathematical match for S/N 2246, so you have the original bumper with roller. (They all appear to have been outfitted with rollers.)
>It has a B and M tag above the center hump on the firewall
Good. Some of these have been seen to have a confusing M16A1 dataplate with "MFG by The White Motor Co." on there, so the Bowen & McLaughlin tag is a help.
>rebuilt 5-53 M16A1 s#2246.
Most of the ones reported have 1952 conversion dates. I don't think anyone has documented the start & stop dates for the B&M M16A1 conversions, but they were probably coming to the end by May, 1953.
>There is numbers stamped on the inside of the drivers rear armor C54634 and under that 38452.
Everything that made up a halftrack would have a gov't part number, serial number & some kind of maker's ID. C54634 would be the part number of that particular piece of armor plate. If you looked at the drivers rear armor plate on another track, you should find that same part number stamped on it. 38452 is probably the serial number of that particular plate, & would be unique to it. Autocar is said to have obtained its supplies of armor plate from either Disston or Mosler. In general, they would stamp their mark in the armor. Don't know if those companies just used initials (like HD for Henry Disston) or if they had a company symbol. Also, the Army Ordnance Inspector usually stamped the "Ordnance Bomb" on the plate, indicating it had been accepted by the Gov't.