As requested I have taken a few photos of my Double rifle.
The barrel is stamped 554 suggesting that it was made in May 1954; the gun comes with the original leather case made in Ulm Germany also in 1954. I suspect from the engravings that it was originally a 201 shotgun, as both sides of the engravings show birds, that was converted to a double rifle with a set trigger added. I believe that there was some kind of export regulations back in the 1950 that prevented the export of rifled barrels from DDR / GDR.
The action is a Blitz style and mounted on a trigger plate. This allows for easy access and regulation of the trigger weight just removing the screws on the bottom. The set trigger can be adjusted by regulating the small screw on the front trigger.
The double rifle keeps the shots relatively well together at app 50 meters, where the difference is between one and two inches, I suppose that I could find a load that would regulate better.
The caliber is 7x65R/7x65R, 7x65R/16 and 16/16.
Please note that this is not an exhibition piece, I use this gun for all kinds of hunting and quite a lot of clays. I usually take 4 rounds of skeet every Saturday. I did shoot some national combined competitions in Poland last year with this gun and did quite well. The advantage of this is that the double rifle feels a lot more like home when I use that same gun to shoot several thousand shots every year. The cost of the caliber 16 cartridges is a bit higher than for cal 12.
As we are only allowed to use steel for hunting and clays in Denmark I use a 24 gram steel shot in size 7 for the clays and the "old" Merkel doesn’t complain about the steel, event it was made for traditional lead shot.
I shoot the double rifle quite often, just for fun and practice, I have the great fortune that I have my own 200 meter range, (Properly approved by the police every year) and I have an ever growing pile of brass in 7x65R so I will probably start reloading some.
My wife complains that I spend more time with my double than with her, and I suppose it is not far off. As you see from the picture she is eager to help with the dirty work.

Best regards
Granhaven , Peter Frost Hørlyck