To the OP: I would avoid the 24 which, as another poster noted, is actually a Minolta lens. The publicity literature of that era included lens element design diagrams; the Minolta 24 and the "Elmarit" were identical. I suspect that maybe the"Elmarit" was assembled and inspected in Germany rather than in Japan but I'd buy a genuine Leica lens, the 28 or 21. NB: All the telezooms Leica offered at the time were also basically Minolta lenses. E.g. a Minolta 80-200 f4.5 was $250 while the Leica 80-200 - identical lens design! - was a thousand dollars more, $1,250. Is assembly and inspection worth 4 times the value of the lens when those operations were done in Japan? Not to me.
I've never understood this "it isn't made by Leica in Germany, therefore it must be second rate" attitude.
For a period in the late 1970s/early 1980s, I had Minolta XD series SLRs and a complete lens kit, including the Minolta MD-Rokkor 24mm f/2.8.
Yes, the lens design was identical to the Elmarit-R 24mm f/2.8. Whether the Elmarit-R was actually produced in Japan by Minolta or assembled by Leica in Germany (or Canada) I'm not sure. And no, the Minolta and Leica lenses were not identical beyond the optical design; they performed quite differently.
Having had both, the Leica lens is far better made and performs like a Leica lens ought to, with less evidence of decentering and better flare control. It produces the same color and quality as the other lenses in the R range. I use it on both the R8 and the Sony A7 ... it is terrific on both. Solid, precise, sharp throughout the range. An excellent Leica R lens.
I mean, what the heck? Leica introduced the lens in 1976 and never changed the optical formula, kept it in production and in the catalog until they closed the books in 2006. It went through two mount updates (original to 1990, ROM update possible to 1996, then with ROM to 2006). They must have thought it a decent enough lens to keep it in production and without any optical change for 22 years.
The 28mm and 21mm lenses each went through a few optical revisions along the way. Having used a 28mm v2 lens, it's great, but not substantively different in quality from the 24mm. I certainly wouldn't avoid it, even if the series 2 Elmarit-R 28mm f/2.8 might be the gods' gift to 28mm lenses for Middle Earth...
G
