The knife you refer to is a rare pattern. While some were marked as you state 51OT, it was generally refered to as a 504. It was only made for a couple of years in the middle 80 tys. I do not know why it was made for such a short period. It has always been a favorite pattern of mine and the closest that Schrade has made to a sunfish or elephant toe, pattern ( I say closest it is not the same, One blade lockback ect). The one you refer to is the one under the Old Timer line. This one is indeed carbon steel, as are most old timers ( The old timer line is carbon steel and the Uncle Henry line is stainless. ) This pattern was also made in stainless steel Schrade + with micarta handles and was one of the patterns used in the president commemorative set produced during this period.( This series was sold through American Express and this pattern had a picture of Andrew Jackson with blade engraving.) It is a nice knife and getting hard to find. I hope this helps Lt.
