I remember that someone used to make a printed zone sticker to put on a Weston Master. I don't know if they ever made a meter with an original zone dial but it wouldn't surprise me. It would have been easy enough to do and Ansel was responsible for selling a _lot_ of Master meters.
It is still possible to obtain the stick on Zone Dial as far as I know-- I bought one for the Pentax Spotmeter V from Calumet U.S. and I believe they produce one for the W.M. V exposure meter.
What's the difference? I think my US Weston was made in the UK -)
Quite honestly, I forget. But I've had two meters with the same number side by side -- V, I think, but it was 15-20 years ago -- and they're consmetically different and, if I recall aright, slightly functionally different too.