Released 1986: The C64C is a redesign of the successful Commodore 64. Due to the light color and the slim cabinet it can be easily distinguished from the original C64 (“Breadbox”). According to the technical specifications there were no differences
Released 1990: geoRAM is a 512 KB memory expansion for the C64 and C128 from the company Berkeley Softworks. During the chip shortages of the 1980s, Commodore could not produce enough of its RAM Expansion Units (they eventually cancelled them).
Released 1982: The Commodore 64 CP/M cartridge was released shortly after the introduction of the C64 itself. The cartridge contained a Z80 CPU to run CP/M 2.2 operating system. The CP/M cartridge was cancelled around 1983 I think, and reportedly will