Definitely from German editors, as they call the people who engrave flats.
As Simon mentioned, the bases can help identify the maker and his catalog. Sometimes it can be something engraved on the base, in other cases, it can be the shape of the base-diamond-shaped, oval, rectangular, and so on.
If we can't provide much more info here on the Planet, I can recommend the Treefrog Toy Soldier forum as one place to search. I am fairly certain that there is at least 1 thread there about identifying flats. Treefrog's URL is
https://forum.treefrogtreasures.com/
Another forum that might be of help is the Figure Mad Forum, which is a German forum I belong to. There should be a couple of threads there that deal with identifying flats. Its owner/admin is Martin Rohmann, who is a member here at PF, too. The Figure Mad Forum is at
https://figure-mad.com/smf2/index.php
Finally, you could also take a look and even email the staff at Berliner Zinnfiguren. The owner is the proprietor of a catalog of flats that his father produced, and which he still produces. He also sells other brands of flats from various makers. The URL is
https://www.zinnfigur.com/startseite/
Hope that helps, prost!
Brad