The D5 is the evolutionary successor to the D2.  As the D2 continued its run into the 1970's, there were increasing concerns about its awkward system of lens cones required to accommodate different focal length lenses. The D5, with the extended bellows previously available only on the D6, eliminated the need for lens cones and provided a simpler lens mounting system. Other significant changes included the enclosed column, and an improved lamphouse lifting system. 

Since the D5 was introduced after the DV Condenser Lamphouse and Super Chromega II Dichroic Lamphouse had become available, it has only been supplied with those two heads. Originally supplied with grey finish lamphouse and carriage, late production units were black.

The venerable D5 ultimately outlived its intended successors, the D5500 and ProLab II. 

Used Advice: A reliable workhorse, but older units with heavy usage should be closely examined for excessive wear and tear as extensive work may be required to bring them back to factory specifications.