Interesting ... you'd have thunk that it would have been on the list of bells, gongs and whistles for an enhanced gun.
My Gold Cup has a Swenson ambi from it's days of wearing a ported Clarke 'Pin Gun" barrel I used in IPSC. Now it's in deluxe 'street carry' mode with the original barrel. It also has a Pachmayr 'mud flap', mag well funnel, Millet rear sight and King beavertail, none of which are on my R1.
While I really appreciate the goodies on the 'Cup (especially the trigger!), I find I spend more range time with the R1. It's not stock GI by any means, but more of a 'bread & butter' gun. If I could legally pack a gun, it would be the R1.