It could be just a somewhat failed f at the end. Also, I wonder if it’s actually Rüff, as there’s a curve on top of it. The letter ü (as well as ä and ö) developed from a small e above the letter, which was then gradually stylised to what it’s now.
Doesn’t the arc above the u of Ruff mean that it’s short, i.e. no umlaut? I’ve seen handwritten letters (including postcards from Paul Maas) that use that convention, only with a shallower curve. (Besides, surely the name would be Ruff not Rüff wouldn’t it?)
The Ruft pro Ruff really was a mistake. I don’t know what to make of the º above the /u/, except to note that it reappears, as a micron-shaped diacritic, over the other instance of the name, and that the word Durchleütigesten does have a modern-looking umlaut over the /u/, and the two are sufficiently different that I wouldn’t expect them to be the same symbol.
Yes, you’re right (= ihr habt Recht), it’s not ü in Ruff. I didn’t notice the spelling Durchleüchtigesten with ü, but just thought it’s badly printed with spectral traces atop the letters. It’s interesting as this is of course not the modern spelling (heute, Leute, leuchten, Häuser, all nowadays pronounced as [ɔɪ] {differently in the 18th century?}). The breve sign (or indeed ring?) is singular, though I don’t disbelieve it’s been a convention.
I can’t quite make the last word out, but it’d appear to be approximately the same Sirffey as earlier. I read it as Kaisser von der Sirf.. (‘Emperor of the S.’), with the last letter (or two) unclear to me (umlaut above — ä??).
