Not really on an E. Dotter. Mainz was just across the thread of the stream of the Rhine from Wiesbaden, but pure conjecture would be that he was the relative, possibly the son, of Johann Dotter of Würzburg who had the title of Königreich Baiern like Georg Greiß of München circa 1840. Also I would guess he was an apprentice of one, if not all of the following Mainz büchsenmacher firms of F. Blanck(who preferred Belgian pattern welded tubes), Gebrüder Lindenschmit, Silvester Trenelle, with Trenelle being a likely choice as he peddled pistols and I've seen a few pistol offerings of E. Dotter. Maybe he may have known Daniel A. Nohascheck of Mainz. So I'd say he was active in the mid 1800s. Maybe Axel can enlighten us with something other than Dotter was a country gunsmith. I assume it is a hammergun so what is the lockup type?
Kind Regards,
Raimey
rse