Although is't not really 'stamps' on stamps, it's surely related.
This 2010 sheet was issued by the belgian postal services, in a series of old and new postal vehicles.
Two trains are shown, as well as three vans. The eldest on top, the youngest at the bottom of the sheet.
In the border of the sheet, two pictures of real vans are shown.
The sheetlet misses some information about year or type of car/train, but for the rest, it's another beautiful sheetlet. The "1" indicates that each stamp is supposed to be used for a normal letter (max. 50g) within Belgium.
The sheets were printed on 6 plates.
The number of the plate is shown towards the left hand bottom corner of each sheet.
Each plate was used in equal numbers.