Found this and thought it may appeal to some, basically someone with way too much time on their hands has gone and identified almost every R-series droid in the original trilogy.

R5-K6 makes an apperance as well as a R2-X2 (which looks a lot like the R2-F2 we know)

Anyway check it out at the link below if your interested.

http://www.angelfire.com/droid/astromechs/page10.html

Whoa! You were right. Way too much time on their hands. I scrolled down page after page and then spotted the link to check out the Imperial droid page. Good grief!!

Some old guy on the street told me these are not, in fact, the droids we're looking for.

It's okay, it probably had a bad motivator...