The article is probably referring to the action changes made after reunification. Flat spring to coil, etc.
I would consider Merkel's to be of 3 types. Pre-WWll, Communist era, and post unification.
There are plenty of differences denoted to bracket the guns this way. I don't remember if the articles were by Doug Tate or Clair Kofoed, but they were in SSM, around 2004.
I looked at a 1950's, 303? that had excellent deep relief engraving. But I was saddened that the firing pin holes were so whopped out that it was a firing pin eater. The remedy was bushing, but I was told then that the geometry of the strikers on that model routinely ate away the holes in the breech face. Something to think about in O/U's.
