does any know what these barrels fit.

Pictures are to fuzzy to read anything. What are the proof marks on the barrels. the one thing I can tell is the extractors are missing.

pics added

From what I can read it is a set of rifled 20ga Belgium o/u barrels made in 1954. Looks like it might have been built to hunt boar with slugs.

Here is the Belgium proof mark guide.

https://www.hunting.be/wp-content/uploads/2020/02/Belgian-Proof-Marks.pdf

As far as what they fit, is there no writing on the tops of the barrels. You might want to take your question over to the double gun site.

https://www.doublegunshop.com/forums/ubbthreads.php

They also have 3" chambers, Erich. They look a bit rough, not great craftsmanship, almost like a Baikal.

I think they're later production. 3" 20 gauge guns were introduced in 1954 by Winchester and were not common until about 1958...blossomed in 1960's.

Interesting that the chamber length is marked at 75mm instead of 76.

the barrels are both rifled, and 7m/m a 307 winchester case will not chamber and the rim is too big. no markings on the top.

Time to go over to Double gun and get some real experts on Belgium guns look at the pics. It then looks like someone converted a set of shotgun barrels into a double rifle, not unheard of.

Also time to do a chamber cast to determine cartridge.

I just want to sell it once I know what they fit.

I don't want them.