I've been told that it's actually modeled on the Merkur 36 which is no longer made. That was a 3-piece razor with the same head.
I realized that while this is an answer, it doesn't really answer Jim's question. My apologies.
@Tanuki will doubtless chime in, but my experience using a rather "well-loved" vintage Merkur 37 alongside a German 37 feels a lot like the same razor. The RR version has the scalloped cap so is modelled on the post-1970 Merkur, but while they made some changes to the tooling I don't believe they fundamentally changed the design of the razor.
The main differences in how they each feel, to me, are determined by the handle. The two-piece Merkur has the same handle as the 34, which is just a tad light and short for my taste. I tried three RR handles with the German 37: their "HD," "UFO" and "Bulldog" handles. The HD feels just like the Merkur only a little heavier since it's solid stainless. The HD being short makes the razor feel a tad head-heavy (like the Merkur); the UFO handle gives me a neutral balanced feel; and the Bulldog while long enough and certainly well-knurled also makes the razor feel handle-heavy.
Oh, and I notice there is a Merkur Super Slant on offer elsewhere. I can't pick it up, being outside the US, but it seems a decent razor at a price I'd jump on in a second if I could. It'd be nice to see it go to one of our brothers.
O.H.