The earliest document showing Master Mariner I have is from 1957...
By: blomman Mr Blue : May 9th, 2016-13:42
And at that point the buckles were not signed on the outside. Possible it were signed on the inside, but not sure if LC started to sign their buckles at the same time as JLC (circa 1960). Here is an ad from 1957... And here is a inside signed buckle that ...