Leica Elmarit-M 21mm f/2.8 – Cod. 11 134 / E60

Produced from 1980 to 1997
The 21mm f/2.8 is the 21mm first lens actually made by LEICA, instead of the earlier Schneider lenses merely resold by LEICA. It was made in Canada.
It is a retrofocus design, meaning that the back of the lens doesn’t poke out as far as previous lenses, so TTL metering works on all cameras that have TTL metering. You get TTL metering since the retrofocus design keeps the rear elements further from the film, but the literature suggests that you get more distortion in return.
Early versions (Elmarit, 1980 – 1985) took 49mm filters, while later ones (Elmarit-M, 1985-1997) took 60mm filters.