I've got a pretty good idea. It's a crazy long list. This list is based on personal experience and machines that are listed in parts lists.
*103 - Classic Red
503 - Classic Red
*103CB - Brown - Cleavland Browns
500 - Black & Yellow, Series 500 (some series 500 models were black & red, many different model numbers)
172 - Classic Red, Plus
*80510 - Green, Plus
*513 - Black, Signature Series
*533 - Blue, Pro Series
510 - Gray (never seen one)
08100RED - Red, 3 amp
08100RT - Red? 3 amp
*08100RTC - Red, 3 amp, new style motor, much more powerful than GS Electric models, round bag shape
*12V car vac - Black
12V car vac - Kenny Wallace variant
*Included in my own collection
That covers the common variants. Some came with round nozzle plugs and some with the later permanently attached cover.
A larger list of model numbers can be found here at the link below. Just scroll down to the hand vacs. There are some odd models in addition to those that I listed.
http://www.hescoinc.com/vacuum_cleaner_parts/royal.html