As there are no official, civilian proofmarks (at least you don't mention them), the rifles was certainly put together in America. The custom hardware was availble in the USA. Bought such a "Williams Streamlined" front sight ramp and "Whitworth Express rear sight with base" myself from Brownells in the 1990s. The custom bolt handle blank was also offered by them as "Meier Butterknife Bolt Handle #1207".