Thank you for identifying Elsberger. Here is another of him and Grothaus as well.
Officers of the German Corps under General Louis Botha
Second Row: Dr. W. Vaheutin Lieut. Von Quitzow Lieut. Grothaus (Transvaal Artillery)
Front Row: Prince von Jutrzenka Lieut. Von Zelewski Dr. Elsberger (standing)
The man leaning against the tree is not identified. Note black puppy at bottom right.
From: With the Flag to Pretoria, H. W. Wilson Vol 1 1900 and britishbattles.com
I have at last managed to find a copy of Volume 49 (1896-1897) of "Revue d'Artillerie", Berger-Levrault et Cie., Paris, which includes a detailed description of the 75 mm Q.F. Creusot, System Schneider, mod. 1895, as used by the Transvaal Staatsartillerie.
In the opening paragraph the writer states:
"Le matérial de 75 à tir rapide, que nous décrivons ci-dessous d'après les renseignements fournis par M.M. Schneider et Cie., est celui qui a été livré par ces constructeurs à la République Sud-Africaine dans le courant de l'année 1896".
The volume includes four large fold-out drawings of the gun and its limber. Small reproductions of these were included in an article on Boer guns, published by “Black and White” magazine, Dec 9, 1899, p. 814.
Also included in the article are the following three plates of the breech mechanism. The shell case is considerably shorter than those fired in South Africa, and might indicate minor differences in the mechanism compared with that used by the Staatsartillerie.