I am trying to determine the compression ratio of some M-100 6.3 pistons I have. I am also trying to determine if they are oversized.

What I know... They are flat on top. There are no cut outs for valves. The only numbers I can find on them are under the wrist pins and these appear to be casting numbers from MALHE. There is no Mercedes part number on them anywhere.

The connecting rod has a number on it. It is '1001'. It is a length or perhaps a '10 to 1 compression ratio' indication? There are other number at the bottom of the connecting rods, near the bearing caps, but I think this is the weight of the assembly in grams. There is also a number etched in electric pencil that says which cylinder the piston goes into.

Car was a US delivery 1970 109. Any thoughts?