Well, I'm no expert myself, however, all I know personally is that Oil-tanned leather can be distinguished from other leathers by its waxy surface.
If you're still not sure as to what it is, if you want to send me, say a small sample of it I can tell by that. 2x2" or smaller perhaps??? I f so, pm me I'll give ya my mailing address.
I have a few leads but nothing yet on this leather.