Found this info on a non glass site, so looks like it will not be easy, maybe when Feli has access to student networks...
...the number preceded by the initials 'D.R.G.M.' is not a patent but an utility model registration for a short term (three years that could be extended for another three). With few exceptions, all the files from 1891 until 1934 are lost, and the only information available about a given number is the classification number, title, registerer name, address and date. For example, number 96541 correspond to a 'Kugelpatrone' registered by Brenneke of Leipzig on March 29, 1898 and renewed on March 20, 1901.
I'm afraid that this information can only be obtained at the Deutsches Patentamt in Berlin. Also, you may be able to find old paper copies of the 'Patentblatt' in some public libraries in Germany, USA (Chicago) and probably in other countries as well. Some US libraries also have digitalized copies but these are accessible only to universities using their private network.