The train set bought for Joey has the name Rovex on the box. This was a name used by the Triang company which manufactured OO scale model railways. However, the actual train set in the movie appears to be a much larger Hornby O scale set.
In this film, Carl Moehner's character - a gangster - kidnaps his accomplice's son in order to push this accomplice to reveal where a loot is. And in another gangster film starring Möhner - Rififi - it was the contrary: Carl Môhner's son was kidnapped for the same purpose.