Origin Of Mint Blocks Of 4, International Reply Coupons?

I have been seeing Blocks of 4 of International Reply Coupons of many different countries being offered over the past few years, generally stated as being from the collection of King Fuad of Egypt and being "probably unique in private hands".

The below image is on Delcampe, from a listing by the auction house Christoph Gärtner. The reverse image shows the normal reverses of an IRC, with no additional markings beside a light stain on one edge, probably from glue used to attach the block in an album.

Assuming that these are from King Fuad's collection, where did he get them from? Any information as to the origin of these items would be appreciated.

Hungary

Well yes, I know that this example are of Hungarian IRCs. They seem to exist for many, perhaps all countries which sold IRCs and in several different IRC types.

What I was looking for was some information as to how they came to exist as blocks of four, as the UPU was in change of the printing and distribution of IRCs to each country and would distribute them only as singles.