Aftermarkets are not available AFAIK. Originals are occasionally available on eBay and Gunbroker for a price or three. At one time, for a short time immediately after the '64 changeover, Win offered SG swivel bases that were made wide to fit the earlier inletting but the humps were cut down to accept the narrower modern swivels. I'm not clear on the details but remember getting a 52 Sporter stock from the factory in '69 but the swivel bases they sent were the cut-down ones. The Win 2-screw non-detachable bases are the same dimension and they'll substitute nicely if you remove the swivel bow but then again they're worth quite a bit also and it would be a shame to ruin a set. But I forgot, you already have the bases.
The originals were made in at least 4 sizes: 7/8"(carrying strap, most often encountered and cheapest), 1"(small sling, 2nd most common), 1 1/8"(Marlin deluxe, VERY seldom encountered, most collectors don't know its details 'cause they've never seen a set) and 1 1/4"(Win NM SG, very rare and highest-priced). They were also offered separately as an aftermarket add-on, albeit with studs rather than 2-screw bases.
SARCO at one time offered a reasonable substitute that originated as a detachable military swivel in one of the Scandinavian countries; I believe that Mark knows the details.
Here's a pic of some SG swivels, original and otherwise. The Scandinavian swivel is the one on the bottom left. The middle swivel is a 7/8" Win and the swivel on the right end is a modern narrow 1" one.
I like these swivels A LOT and have used them for many years, however they're getting so expensive that I can't afford them any longer.
Regards, Joe
