Rifles, of whatever model, were not routinely rebuilt or refinished unless an initial inspection showed it necessary, so a WWI rifle could well have retained its original finish (and many did). Late WWI rifles were also Parkerized at the time of manufacture.
There would be a lot more M1917's in the US had not some 1.1 million been sent to England in 1940. FWIW, 500,000 were shipped in June 1940, a second shipment of 300,000 went in September of that year, and the remainder in October.* Many were brought back by US dealers in the 1950's but many more were distributed throughout the world to US and British allies. Some have turned up in Afghanistan, even being used against US forces nearly a century after they were made. Some were issued to the Vietnamese home guard during the fighting in that country, leading a really sharp reporter for the Washington Post to fill a couple of pages of shock and horror reporting that while US troops were unable to get the M16 rifle, the US was supplying the even newer "M17" rifles to the Vietnamese.
Jim
*Since those rifles were a good part of the US war reserve, and M1 production was slow getting started, Army Ordnance contracted with Remington and Smith Corona to make new rifles of the M1903 and modified M1903 pattern (the M1903A3)..
JK