Thats a relief - I heard of several people who have found an old gun in the loft not realising they were committing an offence by possesing it - I would not want to see someone tripped up just for the sake of mentioning it.
It looks a nice bit of kit - it looks a substancial calibre and do I see double set triggers? I bet it will shoot well as long as it wasn't left dirty all those years to rot the rifling!