Just to add to this with the help of jP (Springer) I determined there are 5 total dial variations for the 16700. The serials listed with each dial aren't necessarily comprehensive either as the sample size wasn't huge.
Mark I
1st Dial I found. Found in R, L, E, X, S, T, W, U Serials
Mark II
2nd Dial. Found in L, X, N, W, S, T Serials
Mark III/Mark IV
3rd T<25 Dial/1st Swiss dial. I guess we can consider it the 3rd and 4th versions. Found on U and A serials.
Mark V
Last one. Found on T and A serials.
