JeffSteve - I believe it is Karl Ritter von Martini. https://prussianmachine.com/akb/martini.htm
O KNo - feel free to pass it along to them, Steve!
They did contact me after a whileNot that I have spent much money at Der Rittmeister after all these years. I did reply with the correct answer as soon as I got that email. Not because of the $50 but because for some with particular areas pf interest, that is a very commonly seen portrait. Der Rittmeister, however, did not have the courtesy to reply. But as Steve said, what can you buy for $50 at that place anyway?
Elwyn