Rolf,
Maybe yours is from a W111 Coupé?
The speedos look identical to me (with the exception of the gear transmission ratio, the "Wegdrehzahl") but probably they aren't - Maybe there is little less space in the 111's instrument cluster and therefore the stud is shorter and the bracket is different?
The only differences I know are the speedo housings (metal vs. rubber) and the early 220 SE speedo has different numbering in the kilometer version. But other than that .... :?
Will compare the original 1964 speedo with the non-original 280 SE Coupé speedo this weekend when i'll get access to the parts ...
Achim
(W113 parts collector)