Although the Scott Catalog does not list any varieties for this issue, according to the Deutschland Specialized Catalog for Bohemia and Moravia, this stamp comes in 3 varieties (Michel #34)
34a – schwarzlichgraublau (blackish gray blue)
34b – schwarzlichgrauturkis (blackish gray turquoise)
34c – schwarzblau (black blue)
Now these colors seem close, but here is another copy for comparison:
Luckily, according to the catalog, you can at least differentiate the 34a from the 34b and 34c with a frame line.
Examine the following closeup and the first stamp (34a) has no frame line extending to the outside line. The second (either 34b or 34c) has the frame line. Also, 34b and 34c are supposed to show some white blocks in the upper left corner (see arrows) – But these seem inconsistent.
I examined quite a few of these closeup and it seems that this little line extends at various lengths – note the following:
The line seems to extend anywhere from 1/4 of the way, to halfway out. Also, the last example you can see the white better in the upper left.
Unfortunately this doesn’t help me identify the 2 colors – But I don’t think they look turquoise so I will guess my examples are all of the 34c variety.