As a "Dodgy Diana User" (thank you, BBS), I have no idea at all what that is.

The 24 is a mid-80s replacement for the 25 and 27, sharing base design with the 34. A number never used, I believe, before 1984.

That's not that.

The stock looks almost home-made. The rear sight looks pre-WW2.

In addition, most post-WW2 German airgun stampings went "made in Germany" (early 50s), made in Germany west" (circa 1960), "made in west Germany" (mid-60s onward?).

So you've stumped me. It's either incredibly rare and previously mostly unknown, or some kind of "bitsa". Maybe, indeed, a fairground rifle.

Weird.

And, no, I don't want it.

Any date stamp on it, back on left side of the upper receiver, above the trigger group?

Weird.

Did I say weird?

Weird.