WWII Croatia (Ndh) Stamps

*** Moved by Staff to a more appropriate forum. ***
I posted this in the wrong forum, so I am reposting it here. These stamps are Michel Catalog M1 and M2. I find them interesting and have attached scans of each. There are many varieties to collect as well. I would love to hear about what members think of this kind of stamp.

The correct forum, probably, would be: https://goscf.com/f/28 rather than this general philatelic discussion forum.
An argument could even be made for https://goscf.com/f/29 but I am not a big fan of this back-of-book Scott ignorance when stamps had genuine use as prepayment for postage.

Maybe, you could elaborate on 'this kind of stamp.'

Sure. These stamps are not listed in Scott, which is completely inadequate for WWII European stamps. Michel is the best source for information in this area. M1 was issued to troops to be used on parcels weighing 1 Kg or less that were sent home by soldiers. M2 was the same but for parcels up to 2 Kg. M1 had a printing sheet of 4 panes, each pane 45 stamps (9x5). M2's printing sheet size is unknown, but a pane is a normal 100 stamps (10x10). M2 can also be found with an overprint, "FELDPOST" diagonally printed in red. The normal pane of 100 was quartered into "panes" of 25 stamps and then overprinted. So four different panes of 25 stamps exist for overprinted stamps. The overprinted stamps never were issued to soldiers; and, according to the German expert Dr. Rommerskirchen from the '70's, were from presentations folders given to important people. There are recognizable constant plate flaws on both M1 and M2, along with imperf, partial perf, missing colors, set offs, etc. If people are interested, I can provide scans of these. They are completely specialized issues, hence BOB. Phil