Pete it may well be in proof but it has been known for the Proof house to mis stamp the odd gun .If it was a very good sleever and not declared as such it may have accepted as a reproof. The London proof house, for a short time in the 80's if memory serves, did not stamp sleeved on guns submitted but stamped the bore size on the tubes in front of the sleeving joint.They also marked as a reproof if the original marks were still current.
I suppose that as with many things ,your view point may depend on weather you pay for having it done ,or, your payed for doing it.I personaly have no predudice against sleeved gun ,but fitting multi chokes to a nice doublegun . Now that to me is a real good way of dropping its value .
