From time to time Lesney introduced features such as operating suspension and plastic window inserts into their range in order to increase play value for their models. When the first model with side opening doors was introduced in 1963 (the 53B Mercedes Coupe) they probably invited the scrutiny of competing manufacturers who may have secured license trademarks on various aspects of diecast model features. The opening doors were credited to Solido as the original licensee apparently on subsequent models. You were correct, as indeed the later versions of the 53B with fine black plastic wheels were given a patent number on the base. I am just wondering if that was due to the way that the doors were secured on to the body. The 22c as the next model to feature opening doors also had a patent number added to later production. The early version of this car is a hard to find variation in my opinion.

The patent number 983558 stands for opening doors, and it was cast on the bases of all MB Miniatures featuring opening doors from the mid-1960s until the early 1980s. The earliest of them were 53b and 22c as mentioned above, plus 71b Jeep Gladiator. The earliest versions of these three models came without the number, but it was added later on. The last completely new models to be issued with this patent number cast on the baseplates were MB 076 Mazda RX-7 and MB 077 Datsun 280 ZX, both introduced in 1983.

Some models have crossover variations on which the number is still cast on the bases although the doors do not open. One of these is the MB 116 IMSA Mazda RX-7 which shares its base casting with MB 076.

The French license text as mentioned above ("opening doors - license Solido") was printed on the end flap closers of all except the earliest D type boxes for 53b and 71b (from about 1965 onward) and of all E and F type boxes for models with opening doors. With the G type boxes first issued in 1970 this feature was discontinued.

There were also two different types of door holdings on the Pontiac as I noticed. The first type did not have the metal stripe which forced the doors to swing back when you started to close them. The interior was also modified in this section where the metal part was placed. I believe the version without metal stripe was licensed from Solido, later they made their own system. The metal stripe was used on all MB miniature models with opening doors up to the BMW 850i (which is still in production) but the Collectibles got yet another type of mechanism (not as good as before IMHO). Another long tradition has almost come to an end.