[DonVoigt]

I believe that no "j" suffix in military lugers is somewhat more than conventional wisdom.
If you add the jumbled time of post WWI to the mix, there are two "j" suffixes reported in Dwight's commercial data base, along with many "i"s.

These could be true "j"s or reporting errors or use of a "j" stemple instead of "i" when one broke and could not be replaced immediately.

A possible/logical "reason" for no "j" is that I and J are used or were used interchangeably by the Germans in that time, making use of both a record keeping nightmare- when written
in script it is near impossible to tell one lower case letter from the other. JMHO

I'd like to see a picture of a "j" for sure.

As to the Z having a cross, yes a Capital Z, but no on lower case.
I agree Erfurt did not reach Z , so I don't know what the op's mark really is.

It does not follow that it is a "j" as it is not shaped as a j nor does it have a "jot".

Next closest in my mind is a "g".

I will post a picture of lower case German "z"s as soon as I find the reference.

That suffix surely is odd.