Can you identify this rimfire bolt?

[Willy Tincup]

See pictures below:
Now believed to be German made but not definite. Calibre is larger than .22 and appears to be 5.4 - 6 mm range.
My 7mm rf ammo will not fit into the recess in the bolt face, a bit too large.
I could not get a clear shot of the markings on the bolt, most are very light. There is a letter B with a figure above it, not a crown but something similar. There is a small circle similar to the JGA symbol but the letters [if any] are not legible. Any ideas? Thank you

 

[Buster95]

Very curious bolt.

 

[chanman]

9mm Flobert garden gun maybe?

 

[Walther_PPK]

Something in .25rf maybe?

 

[Willy Tincup]

I think something about the size of the .25rf but probably with a metric designation if it is European manufacture........and the stamping with the letter B under a polygon looking object shows up in the German proof mark info.
If the stamped number 24250 is a Serial number as I suspect it indicates there were a fair number of them made and I am hoping that someone will recognize some of the unusual features of the bolt and its handle.

 

[gaff]

It is a Simson Prazisions-Karabiner bolt. JGA may have had a similar model. If your thinking to sell it, or need the rest of it send me a PM.