The 156OT Little Finger was only made for a few years, 1979-1985 so they are relatively uncommon today. To my knowledge, they were all 1095HC steel and there was no Uncle Henry stainless variant. However the pattern was later used for a few limited editions with both staglon and genuine stag handles and stainless blades, so marked. Also, this was before the time when they began to make running changes of the steel in the Old Timer lines to stainless, without changing the stamps, packaging or catalogs to indicate that it was a stainless blade.
Generally speaking, if a blade after circa 1973-76 has a "+" mark, it is stainless. Absence of that mark does not mean that it is not stainless. Also, while Schrade+ steel was historicly 440A, in the later years it was changed to 420HC.
You can test your Little Finger steel as mentioned, but if it is a as-new example that you are keeping to collect and not use, you may not wish to cut acidic fruit. You can perform the test on an obscure spot of the exposed tang instead where it will be easier to polish back off if done quickly. In my experience, on pristine carbon steel Old Timers the first place any patina/handling marks show up is on the exposed full tang, not the blade.