Hartkopf/Schmidt & Ziegler

[beresman]

I purchased this equal-end pen knife to add to my collection of pearl-handled knives, but having it in hand I am now a bit confused. The main blade is marked "R HARTKOPF GERMANY", with what appears to be "1a" on the main blade. The secondary, however, is marked "SCHMIDT. ZIEGLER" with YO1A and "MEXICO" under that. If it has been cobbled together from parts, someone did a really good job--the pins are nice and flush, there's is no gap on either side of the back spring, and the whole thing, while obviously used, is really solid. It's about 2-7/8" long.

Was there a connection between Hartkopf and Schmidt & Ziegler? And I thought Schmidt & Ziegler was a German company; why would it be marked "Mexico"?