Well I would expect it to be deactivated if it was put there by the Airfield Explosive Ordnance Disposal as they have loads of bombs, rockets, missiles in their training arsenal. Having said that, I the guns on the ZSU-4 didn't appear blocked at the muzzle end, nor were any holes cut into the breach area or along the barrel. If it is deactivated it must either be welded or cut inside the breach area which I couldn't see. Shame this sort of thing is stuck out on the perimeter where it should be in a museum!

Regards
Nexx
BTW Tony, the airfield is perhaps around 50 miles from Derby.