There are three ways to determine choke if its not on the barrel flats. newer merkels show letters denoting choke, but yours predates that system. you can do it the true way> what % of pellets inside the 30 inch circle at known distance, but that can also be affected by load and pellet sizes.
You can use a handy choke gauge, that ASSUMES the nominal barrel diameter ahead of the constriced area is NORMAL and AVERAGE for your gauge. these are usually made of brass, with tapered or stepped diameters. I like these cause they are more accurate than the first joint on my pointer finger, that fits into mod, but not into full, and goes to second joint for IC. but thats for 12 gauge only.
You can use a barrel mocrometer made for that purpose, that will show the thousandths of inches constriction, which varies by gauge.
go to galazan website or brownells, and buy yourself the brass stepdown cylinder, and you can get PRETTY CLOSE. based on year of manufacture, I will venture that your Merkel is going to be tight, very tight, or tighter yet. I have opened up one of the barrels on several of my early post war merkels, to good effect.
best of luck. your gun was made during one of the absolute best years of Merkel history.
