Why, please, would a gun be required to have a re-proof after the only work being required being putting it back on the face? I have never in forty plus years of shooting had any gun that was only "off the face" ever require re-proof. Re-proof is needed if the internal barrel dimensions are no longer are within the allowed margin from when first proofed. Or if the chambers or (so the Proof House seemingly requires) the forcing cones are lengthened or are elongated.