Challenge on to identify this gun

Lancashire Police's armed response officers brought a lighter tone to a serious matter after a gun was handed in to them on Saturday.
The gun handed in to officersThe gun handed in to officers
The gun handed in to officers

They took to social media to ask for suggestion as to the identity of the weapon as they posted this picture of it.

A message on their Twitter site said: "Lovely little gun found this morning and handed to us -10 arv points for correctly guessing the type of gun!"

Early answers from followers included: "It’s not a gun, it’s a Broomhandle Mauser", "British Bullodog", "Belgian Bulldog" and even "Spud"