Between WW1 and the appeariance of the modell 200 serie also known in germany as modell "Taube", "Pigeon" ca 1925 Merkel used an other modell number serie at the guns. 160-163 at 0/U shotguns and 155-157 at the combination guns.
160 had a standard engraving and with anson & deeley lock
161 as 160 but with ejektor
161 A. ejektor and better engraving in english style
162 as 161 A but with false sideplates with nomally, hunting scenes.
163 sidelock type Holland & Holland. Top of the range.
The 160-163 had not the three part forend as were typical of the Gebrüder Merkel we are knowing up to the new models today 2000 serie. I have seen a modell 161 with insert comination barrels that once was offered by a USgundealer

155 system blitz with hammers on bottom lockplate
156 as 155 but with better engraving
157 anson & deeley lock and better engraving

The modells of the combinations gun 155-57 were a standard offer in Suhl at that time then a lot of gunmakers had them in their catalogs. The modell had only one "Kersten" at the barrels as the standard greener lock for side by side. And whole forend.
They could also be delievered as double rifles.