How many different variants are out there?
If you consider all needle system variants in the assault badge, there are about 370 different variants expected, without the distinction of silver and bronze. Both should together yield about 650-700 different variants.
There are currently 178 variants and 4 replica on this page.
When was the first and last proven awarding?
According to “Awards of the German Reich 1936-1945” by Kurt-G. Klietmann – p. 109 “was the first award on 28.05.1940. The last known award (documented by a certificate) was on the day of the capitulation of Germany on 08.05.1945 (Infantry Assault Badge in Bronze).
How many manufacturers of infantry assault badges were there?
35 proven manufacturers are known so far. At least 10 more are suspected. So you get to at least 45 manufacturers, which also explains the variety of variants.
How many infantry assault badges were awarded during World War II?
That’s hard to say, but according to “Lexikon of the Wehrmacht” there were about 941,000 awards.