I don't know anything about the gun or seller, just that this is only the second one of these I have seen advertised in the UK in 17 years.

An interesting sidelever design with direct loading and a sliding compression chamber, it has a spring-loaded barrel, for what reason I have no idea.

More common in Eastern Europe as a recoilling target rifle, Haenel sold very few in the UK and they are very rare.

https://www.freeads.co.uk/uk/buy-sel...w#.XDOhgFz7SUk