It's certainly possible it's also by Murray, but pics are definitive. As far as deciphering, it's a long process that starts with a general guess. that's how this thread originated, the early letter codes weren't known, so they made this thread with ballpark figures. Now, years later, we have a list, from a Western Auto parts manual, which has the actual murray codes from 1937-59. The 60s codes were easier for them to figure out, since there's still a lot of original ads and literature out there. Somewhere in the mid 70s, Murray started putting a decal on the seat tube, just above the crankset. It has a month/year date on it.