Some good questions there. Let’s take them one at a time:
There were other Bertrand variants made into the 1930’s and supposedly even post war. Bertrand crosses are scarce and sought after. And equally scarce is information on them. Very little exists.
I will need to get around to posting some Bertand examples from my collection. Stay tuned . . .
The best reference book on the Polish Cross of Valour remains Grezgorz Krogulec’s "Krzyz Walecznych”, only available in the Polish language. A useful book, but sorely in need of updating with better photographs and organization. I know of an updated English language book that is in the works, but still likely several years away from publishing.