Sold. I'm near Austin, Texas.
This is a compact 4/4 rotary four valve C tuba. This one passes the "playability" test discussed recently in this thread: it pretty much gets out of the way and lets you make music. Intonation is easy.
Robert Tucci graciously looked at a few pictures, recalled some memories of the 1960s and '70s, and said his opinion was that it seems to be "a genuine Scherzer instrument, not something put together from available parts." Also, this:
Your instrument looks like something made in the mid- to late Sixties. The Scherzer instruments were all either one-offs or in very small quantities.
Mechanically it's in great condition. It used to have S-links that have been replace by sturdy DuBro connectors. The valves are light and fast. The slides all move easily.
There are some little scratches and some nicks and tiny dents, but overall it's pretty attractive.
Here's the sale listing at the old place where I bought it in 2020. That thread has discussion about how nice an instrument it must be, though it's a little hard to be sure if everyone was talking about the same instrument, since "Scherzer" and variations on "Sander" seem to have appeared in many places. After I got it, I thought it mysterious enough that there's also this thread at the old place with guesses about the instrument's origin.
There's a hard case. The bell portion on the top is not as solid as you'd like if you intend to use it, but it looks like great protection for shipping.
This tuba is compact like a Miraphone 188 (on the left in this picture). The bore is 19mm through the valves, and about 19.5mm at the main tuning slide (both sides). So the bore all the way through is a little smaller than the 188, the 420mm bell is smaller, but the picture makes the bell throat look almost as big. And somehow the Scherzer has a deeper tone than the 188; it's sweeter and less brassy (for me).
And here it is next to a B&S Symphonie. Same size bell, but it definitely sounds more like a contrabass than the F tuba. I used the Scherzer for Eb parts in brass band before I switched to an F tuba, and it did nicely.