Young King Farouk, 20m blue or maybe ultramarine a/38, block of 4 mint, even comes in a rather old transparent paper envelope ^^

Just received them from a friend, but cannot find any mention of them, I can come close but that was a higher number and from a cancelled run.
can anyone help me find some information on these, date, run or maybe worth in case I want to sell?
Sorry, I'm really new at this, not entirely sure what I'm doing yet
Thank you very much