An rare early version Leica Super Angulon M21/4. Much rare than later version M 21/3.4. Original coating . 1646908 dated 1959 fell correctly in the range of 1645301-1647000. Len only with rare back n front cover . Good condition . Photo by M3 with Ilford XD2 400. Price firmed
https://www.kenrockwell.com/leica/21mm-f4.htm
https://www.i35mm.com/gear/leica-21mm-f-4-super-angulon/