The Merkel of the topic of discussion was made under the VEB Ernst THalmann group and one of the craftsmen working on what looks to be an airgun in the pic just may have made the longarm: http://books.google.com/books?id=fTuND6H...;q=&f=false .

Also there are some interesting reprint Merkel catalogues especially the 1937: http://www.cornellpubs.com/old-guns/historic-merkel-arms.php

Kind Regards,

Raimey
rse