Hi, I hope this hasn’t been thrown away because of the crack! I think the depiction of the horse was taken from Carle Verne’s lithograph “Cheval Persan”. This shows a rearing riderless horse being led by a Persian - the position of the horse and its limbs looks the same except small differences in the angles of the forelimbs and the position of the head is slightly different. The rider would have been added by the glass artist. The lithograph and examples of engraved copies on similar glass are shown on page 34 of the article by Walter Spiegl on Dominik Biemann here:
http://www.glas-forschung.info/pageone/pdf/DB_01.pdf . I’m not suggesting it is by Dominik Biemann, shame there aren’t some clearer photos.
Talking about the copying lithographs in engraved glass, the text (via google translate) says “The engraver only had to transfer it to the other medium in miniature. He differed from his professional colleagues only in how skilfully he did it, how he changed the template or added his own ingredients”.