China. The US provided a large number of M1917s and a smaller number of M1903s to the Nationalist Chinese during WW2. Century then brought in a big shipment of these back to the US (in the 1980s IIRC), some which had been scrubbed of some/all markings by the Chinese at some point.
I have a Century M1917, but mine came out of Canada. Those were not scrubbed, but had additional Canadian markings added to the stock. These were mostly used by the Canadians during WW2 as training rifles, often by COTC Cadets at Canadian universities (the Canadian version of ROTC).