You wont see too many of these around. This 19OT was made the same year that the 512OT surfaced.
The original owner of the 512OT declared it to have been purchased in late '89, and it came to him new in the standard tan 152OT marked box. The right box for the knife, acquired later from a friend, had a 1991 copyright date. So that gives us a timeframe. Does your 19OT box have a date?
I believe, (no one has given me any input on this so that and 2.00 wont get you a large coffee), that Schrade wanted to convert the OT line to stainless and wanted the buyers to know that the different number meant stainless.
I agree. Given the statements on similar subjects by Ms. Chase, there was an economic incentive to switch to stainless, and according to both her and the former product manager, Schrade was well aware of the popularity of the carbon steel, as well as buyer resistance to stainless, particularly on the Old Timer models. My opinion (

) is that these knives with associated boxes were test marketing items. Whether or not the plan was aborted before fully implemented, I dunno.
Somewhere they decided that renumbering and stamping was far too much trouble and just changed the steel. Anyone have any insight into this?
Ms. Chase did. She bore the ire of customers who returned knives that they found to be stainless because they bought them as carbon. She broached management with the problem, but they changed nothing but more knives to stainless. Perhaps this was during the period when consultants first came on the scene? Again, I dunno.
Both the 512OT and this little 19OT are marked stainless. They were never in a catalog that I have been able to find.
Yes, Schrade did mark this pair SCHRADE+ on both tangstamps and boxes. And the cataloge eventually dropped the references to what steel the Old Timers were made from (late in the game).
Keep your eyes open for more of these knives guys. What Larry and I have, Mr. Levine calls "benchmarks". I located another 512OT a short time back, and Robert Clemente now has that one in his posession. Every one we find and document puts us that much closer to knowing this peculiar piece of the story. Oh, what I would give to hear the explanations from Dave or Deb!
Codger