One possibility to distinguish between our different Fritz Neumann’s is to compare the signature. The following list shows examples of Fritz Neumanns signatures, the source images are linked in the image caption:

Short description: Two prints from one plate, another fox terrier.

Notes: The first is taken from the Linosaurus Blog . Note the mark under the signature, Holsten Gate variant.
The second is taken from Cofart.be . The colourisation above the eye is different. Note that the signature is different and it has a title (”Ali Baba”), no stamp mark visible.

Short description: A kitten

Notes: Taken from eBay . This on got the Holsten Gate variant of the mark - image of it is lost.

Short description: A dachshund

Notes: Taken from Cofart.be . The stamp mark is clearly visible.

Short description: Two dogs, fox terrier.

Notes: Taken from eBay . This one is quite interesting, it’s attributed to Hermann Fritz Neumann and should be quite old. It also features the stamp mark, but in another form: The letters “J”, “C” and “B” are not overlapping, and are put in the middle of the Holstentor .

Short description: An etching after Albrecht Dürer’s “Preying Hands” by Fritz Neumann. Even if the motif and style doesn’t match, the signature does.

Notes: No blind stamp visible.

Short Description: Sailing boats in a harbour / near a shore

Notes: Another maritime subject by Fritz Neumann, on the back is a sticker reading “Echt Aquarell” (Original aquarelle). But this is clearly a colourised print, since there is a platemark.

Description: Another work by our Fritz Neumann, look at the signature and the stamp mark on the third picture.

Notes: Taken from eBay Kleinanzeigen

Short description: A tile with a print called “Am Wind” made by Rosenthal

Notes: Found on lauritz.com . There are many other examples available on the net (Google Image Search ). According to this page , the mark shown had been used by Rosenthal between 1939 and 1956. Another hint from this page is confirming this by the used style of the underline.

Update: Rosenthal answered my inquiry

A signature of Fitz Neumann (1881 - 1919), taken from findartinfo.com . His subjects are mostly Cossacks, he was a painter.