As well, I am not able to identify the maker. The marks are filled with some sort of black gunk that is very difficult to remove - like baked-on grease from a deep fryer, honestly. I am hesitant to really scrub with a degreaser or the like - any suggestions for cleaning? I believe the maker is either Vincenz Neginik or Victor Nuber. Because of the intertwined Gothic monogram, I lean more towards Neginik, as I have found other monograms in the same style that are attributed to him.
In the attached photos, the marks are the best I have without deep, intensive cleaning. The assay letter on the Diana head is a C.
Any help or suggestions?
Thanks!


