The only time I have run afoul of "Out of proof" in the USA, was when I was trying to sell a British gun to a dealer of "good repute". I got an educational lecture about the gun being out of proof, and how badly that affected its value yada yada. Sold him the gun at a much reduced price...shortly thereafter it appeared on his listings at a very high price. Comment was out of BRITISH proof but in excellent shooting condition..so much for that....lessons learned..