Hasselblad lens nomenclature can be a nightmare to try to understand. Hopefully this will give you a good idea....

"C" Lenses are single coated Carl Zeiss lenses with 1/500 to 1 sec Synchro-Compur shutters. Chrome finished lenses were produced from the 1957 to the early 1970's. The switch to black finish lenses starts about 1972.

"C" T* Optically & mechinically identical to the "C" lenses however, the lenses now feature the famous T* Mutlicoated surfaces. A red lettered T* is printed on the lens. Most users feel resolution results are similiar to "C" versions, but flare is much better controlled with T* coatings. Some Chrome finished lenses feature "T*" coatings, but otherwise all are black finished lenses.

"CF" Similiar to the C T* lenses, but shutter change to Prontor, and other improvements including handling/design changes. Lenses do not have self timers. FLE versions exist ( floating lens element ) for 40mm and 50mm

"CFE" Basically CF lenses with an electronic databus connection with the Hassy 200 series cameras and the lens improvements listed unnder the CFI version.

"CFI" Basically CF lenses that are "I"mproved. Flare reduction improvements, design, shutter and other small improvements that were to "increase image quality, reliability and convenience."

"CB" Budget version lenses. Only 60, 80, and 160 lenses made. 80mm lens had one less element than the CF and less performance.
The biggest difference between the old and new style backs apart from some cometic and minor mechanical differences is that the latest style backs have a slot to store the dark slide when not in use.
If you're looking for an older 500CM then you'll be interested in C series lenses ( no point in paying for electrical connections on the lens which the body can't use) C Series lenses without a red 'T" have a single lens coating and have a yellow/green tint to the coating. "T" lenses have up to nine coatings and have a deep purplish appearance . 'T' series lenses usually command more money as they should produce better colour rendition and resistance to
flare.