October 13th, 2016, 05:52 PM
Join Date: Oct 2016
Location: CT / land of the brainwashed
The proof stamp on very early Marlins was a M in a circle. It was on the bottom of the barrel, forward of the receiver. It was then changed to JM in a oval and then in 1986, they went to a JM without the oval. After that date though, it is common to see proofs with and without the oval. (Brophy p.620)
It is also known that some New Haven and North Haven made Marlins have been observed with very weak stamps, partial stamps, stamps in the wrong or a different location and no stamp at all.
My FIL told me how they put them on with a electric stamping tool, done by hand so it makes sense that it could vary. He worked both factorys and retired just before they sold.