Whoa! I completely forgot about this thread and took down the images long ago to make room for posting others elsewhere. I've assumed that because I wasn't able to put in an image using the site server that I'd reached some limit. It proved out when I took some down and was then able to post new ones. Now I have the habit of cleaning up my image list after a while without looking to see if the thread involved is still active. Wish I hadn't done that.
Dozoclown, Remington was involved in the refurbishing of 1903a1 rifles that had been in storage at Rock Island arsenal as their beginning manufacture of the 1903a3 and later a4. They proceeded to the manufacture of whole rifles in order to supply part of the urgent need in Britain for military arms. They mass produced rifles, the first time such a thing had been done BTW, and there would be a mix of parts used in what was considered to be a monumental undertaking. This should allow the possibility of milled trigger guards made by Remington and stamped with their 'R' for use in the lend lease rifles.
They were not installed to the 1903a4 rifle during original assembly. Instead there was a stamped steel guard without removable floorplate made for both the 1903a3 and 1903a4 by Remington Arms. For the 1903a4 rifles a variation of the guard used in the 1903a3 called a "Type 6" which was differentiated by the inclusion of a small 'pad', a U shaped piece of steel spotwelded just behind the front guard screw that was to press against the wood of the stock to 'stabilize' it. Whether this type 6 guard worked and was used in ALL 1903a4 rifles is a question I've had for years as one of my rifles does not have that type.
Anyway, while the 1903 and 1903a3 trigger guard plates are interchangable with some slight fitting they were not interchanged as an Ordnance Department approved practice.
So, yours is not likely at all to be the trigger guard originally installed to your rifle. The milled guard is in my opinion, and I have no doubt in the opinion of at least some of the snipers to whom the rifle was issued, a superior part both for it's strength and for the ability to unload a rifle quickly through the floorplate. Someone changed yours at some time, probably because they felt as I do. It should not concern you too much, I think, because despite the insistance for absolute originality on the part of our dear internet experts no such insistance was demanded by either the people on the Remington assembly lines or the troops in the field (I like the imagery of a roomful of assembly workers each with a bin of the particular part they installed, maybe five people for each part. "Joe" working across the room from "Sam" but both installing the same part and each with a carefully numbered allotment of parts for certain serial number rifles. Joe has his bin run out a half hour before his shift was to end and rather than wait for the correctly numbered part to be brought to his bin he hollers across to Sam "Hey, toss me one of your thing amajigs, Sam, I want to go home" ---and there goes two rifles with incorrect part numbers out of correct sequence for collectors on the internet to quibble about sixty years later.
That your rifle was used in World War Two is almost an absolute certainty because the rifle was in high demand, so to speak, and never in sufficient supply. Broken or battle damaged rifles were quickly overhauled and returned to service by a supply system that worked so well that items taken from service in France might be back in service in the Pacific islands within a month's time.
Is what you show all you have of the rifle?