Blank face

I can see no other way to date this kind of violin than to find an original dated inscription (very rare). Many of Zoebisch's dates appear to be most speculative, too, just based on traditional opinions. The assumed 17th century Pöpel viola from the Germanische Museum is as I recently read in the Kurt Kauert book now put into a later period as well ( from 1664 to after 1682).

This could be Salzkammergut, perhaps. Is it purfled?

Not exactly. This seems to be a reliable Ebner, but unfortunately with a lion head. The essay points out that this is similar to the head of a Schorn (Salzburg) viola, most probably made in an external specialist workshop.http://www.hof-musik.de/PDF/Musikinstrumente .pdf

This feature is sometimes seen at "archaic" style instruments, but usually pointing to either Saxony/Bohemia or Salzkammergut (very similar traditions). I'm not so convinced that the second OP scroll is really from an Ebner, are you sure?

Saxony or Bohemia.

Hard to tell by the photos. The adjuster collar looks german (U channel), the frog seems to be nicely made, the head less. It has a crack between frog mortice and end which needs to be repaired properly. If you think the 150 are "next to nothing" you could take the risk. Personally I'm more with duane....

Usually the collar is turned from the ring or cap in every case and integral part of it.

Not if they are sold for "next to nothing" (in my understanding what's very next); you are free to ship them to me. The OP confusues me a bit, the head looks like Abeille/ brazil wood; possibly frog and adjuster aren't original if so. But this next to... I would invest in a nice silver mounted Vuillaume type frog, too.

Reg. the "Berliner", it would be possible to write a large essay, but OTOH the general description by Jacob is in the main correct - with exceptions. In opposite to Vienna and the old schools of Southern Germany Berlin has not a very important cultural history at all, and it was more Potsdam where Bach met Friedrich II for concerts, but also without deeper impact. But OTOH, after 1871 it was the new capital and attracted therefore many artists and violin makers, too, some better, others less. So it's a sort of mixed bag, even instruments by the same makers don't show a constant quality, I'm supposing that they had to serve the less wealthy public as well to survive. It was Voss, if I'm remembering right, advertising his instruments as "self made in all parts", what sheds a light on the usual practice. There are very superb violins by Dötsch as well as some rather dull, the same with other makers. Maybe the Knorr instruments have a better reputation in America than here, he seems to have had a good export agent over there. Moenning (who wrote the certificate for the Brompton violin) could have been this person, and for the American market it's obviously necessary to have a well introduced brand. There was (or still is) an Ebay seller listing nearly monthly another violin with the P star K brand, so there must be some of them out there, and I would trust only in an expertise of a person really familiar with his work, maybe from Markneukirchen. Hasert sounds very interesting, do you have photos @Andreas Preuss? Some years ago there was one in a Tarisio auction, but of unclear origin, possibly not real, and online is a viol only http://ftp.baroqueflute.com/musicwordmedia/0009/10.html

A sikver mounted bow for next to nothing is always interesting. Post some sharper photos when you've got it!

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To be honest, the old Viennese are IMO the most undervalued, even in comparison to average Mittenwald.

Something like selling a Hamburger in München?

Nothing what would surprise me at all

Maybe there's something we cannot understand about silver dollars.