Spokeholders on the chainstay are sign that you can take your steed the extra mile (prolly a marketing gimmick, but having carried spare spokes bouncing in a pannier in the wilds, a few on the stay doesn’t seem a bad place to keep ‘em).
And so Raleigh put the spokes on stays on high end 531 tourers; & they put the spokes on the right hand stay - perhaps to offer some protection against chain slap?
But when the heat-treated 708 models were built, someone decided that spokeholders should go on the left stay where they would remain unsullied and ready for use, or just because….
I suspect that there was a lot of showing off on the late Randonneur/Royale frames, especially the 708 ones:
~ oversize seatstay caps aren’t subtle but are a statement; “because we can”.
~ the mudguard “pip” instead of a chainstay bridge only saves a few grams, but says, “this frame is so well designed it doesn’t need reinforcing down here”
- spokeholders on the left differentiate the frame from its 531 brethren.
I beleive the Royales were sold as frames (hence the eclectic mix of components on yours?) The Randonneurs went out as bikes & had a mixed but fairly consistent spec that you can see in catalogues.
Not sure on the USA frame number angle - seems unlikely there were two centres of special builds?
Will make a great bike.