I recently picked up a Haenel Model II in .22 cal to go with my Mod II in .177 which I've had for a while. I expected them to make a matched pair but was surprised to see a number of substantial differences between them. The .177 dates from September 1929 and the .22 from November 1938.
Some of the obvious differences are the trigger block shapes, the Haenel logos, the rear sight patterns, the trigger guard shapes, the stocks (is one an "export" style?), the front sights, and the cocking link pivot bolts. There may be more differences internally too.
The rifle with the shinier blueing is the later model, the duller blue/patina the earlier one.