Try posting to the KnightKit forum. Although not hyperactive, there are a lot of folks there who might have a manual they can copy for you. Had it been the R-100A, I could have helped you. The R-55 went up to the ham 6-meter band and often had the T-50 or T-60 transmitter as a companion unit. The R-55 was the "second banana" of the line where the R-100A was their "big" receiver.
The KnightKit site is:
http://pluto.beseen.com/boardroom/t/18370/
Dean