Plates for mopeds were introduced in 1993 and are very similar to motorbike plates in the numbering system and in the look. The main differences are that the coat of the arms of the Republic is printed just in one colour, in blue, and that the first digit is on the top line, while the other three are on the second. The numbering system is independent from that used for motorbikes, so it could happen that two vehicles have the same plate number. The numbers start from 0001 and at the beginning mopeds had the registration number also as plate number; the first number was substituted by a letter when 9999 was reached, in 1998 (second picture).
Moped plates of San Marino are not personal, as it happens for Italian mopeds, but each moped has got its own plate and this avoids the nasty fact of stealing of license plates and of abandoning of vehicles without a plate on the roads.
The first picture is taken from the archives of ALPCA. I need to thank Olav Arne Brekke for the second picture and Denny Busignani for his help about these plates.