Scott Cowley said
Have any of you seen other Winchesters proof marked in Belgium?
Yes I have… at least a few hundred of them. The Belgian and the British governments did not trust that any U.S. manufactured firearm was proofed tested to their standards, so they required all foreign manufactured firearms be submitted for proof testing.
WACA 6571L, Historian & Board of Director Member
March 19, 2014
As far as the British proofhouses went ALL firearms had to be proofed regardless of country of origin. No discrimination against any particular country. Although I have seen several firearms stamped NOT ENGLISH MAKE which is a little snotty. One benefit of proofing is that a lot of firearms are modified at some point in their lives by folks who may or may not know what they are doing. Proofing of firearms at least ensures they are safe to fire.