There was a good article in a MBZ Club mag this Dec in the UK on the OVP relay. At the end of the article is says:

"As far as I know there are at least three different over-voltage relays in circulation. These are the nine-pin type with two internal relays and two fuses as used on the R129, the seven-pin type with one internal relay and one fuse used on early W124s with carburettors or Bosch KE FIE and the diesel models. Later W124s with the Bosch HFM FIE use a nine-pin type with three internal relays and one fuse".

Only number I know is 201 540 37 45 which is the nine-pin 2 fuse one made in Hungary. This now seems to be the one to use when replacing the seven-pin one fuse model - it was for my M104 anyway (note the 2 redundant pins are accommodated in the relays holster but simply have no metal contacts).

Regards,
Neil