classic motorcycle forum

I am going to need to find a S467 107L Smiths Chronometric speedometer for a 1951 Thunderbird I am putting together. I am curious, are there any resources or knowledge out there about all the numbers after these speedometers? do they have to do something with rotation? The bike isn't going to start out as all original, and I am basically just getting parts together to get it running. I will slowly work on getting it to a better state after that point.

it's pretty much a Johnny Cash at the moment. It's a 51, 52, 53...