Unknown Air Rifle

Hi there. Whilst digging through the loft before moving i have come by an air rifle and would like to know more about it. The only markings on the entire rifle are a stamp just above the trigger marked CS23165 and the same number under the cocking handle. Can anyone shed any light on this rifle? It doesnt seem to be in great condition looking at some of the screws. Links to pictures are below for reference.

Many thanks.