Schrade USA identification

[Goatmother]

I've been looking for Schrade lockbacks recently to replace my Puma knife stolen in the '70s. It has been easy to identify the vintage US made knives thus far from the blade stamp as I've looked mostly at LB7s. Now I have seen a "Schrade 29OT Old Timer Mountain Beaver Sr Lockback Folding Knife " and a 310T Old Timer represented as US made and vintage ( they look quite used) but there is no visible blade stamp. Did the US factory actually make knives without that stamp?

 

[Old Hunter]

Here is a listing of Schrade Old Timer knives made in the USA by model number, description and dates manufactured. It may not be entirely complete, but it is the best single page source I have found. OH
Ps I have never heard of a USA made 29OT or 31OT.

https://www.allaboutpocketknives.co...ife-reference-guide/schrade-old-timer-knives/