I googled up "RWS 54" (with quotes) and came up with 2,270 references.
Anyway, though it is not a 48, the 54 is probably similar enough to the 48 so that all references will be useful somehow.
IMHO the BEST of all references for the 54 (and in the applicable things, the 48) is Eddie Colwell's:
http://www.eddiecolwell.tzo.com/RWS-54.htm
try that one.
You can also try:
http://www.geocities.com/ftshooter2000/page2.html
Again, do Google the references and get a mindful of written material. If you have specific questions, I am sure people here will help you.
Good Luck and keep us posted!
Un Abrazo!
Héctor