[Maarten]

The X means the model was commercially specified in Eindhoven but does in no way indicate a particular destination or physical origin. Neither do other letters in the model number, though foreign models were often specified in the country where they were made and sold, for example BxGxx sets were mostly made and sold in the UK.

A set with an X in the model number could either be for the local Dutch/Belgian/... market, the general market or some particular export destination, depending on the execution number /xx behind the basic model number. This also goes more or less for sets with other letters.

The country of origin (mostly country of manufacture) can be determined by looking at the letters in front of the serial number. For sets like this: PL = Leuven, Belgium, E = Eindhoven, The Netherlands (used up to the mid 1950's), A = Acht near Eindhoven, The Netherlands. Acht was the main distribution centre built in the mid 1950's, not an actual factory. Most sets that were labeled there, came from the Eindhoven factory but there were some exceptions especially for second brand sets.

That was a rather roundabout way of saying, this set is indeed from Belgium. I can just make out the letters PL in front of the serial number.

P.S. I can see an execution number on the label, but can't read it. I'm a bit curious as to the destination of these sets. Maybe the OP could post some pictures in which the labels are readable?