Maybe the R just stands for "Registered", could be it is in the database of Registered stuff which can be browsed at online somewhere (ask google or bing) similar to the TM and patents.
If it is then there will be more information as to who registered it, maybe the material and so on, otherwise you might take it to a good jewelery shop or precious metal or scrap dealer who own a XRF scanner and it will tell you exactly with a scan what % of which metals it was made of.
Edit: registered trade mark search engine:
http://tess2.uspto.gov/bin/gate.exe...ish&p_d=trmk may take a while to you find it if indeed it was Registered
Edited by Cointosser77
02/27/2013 10:48 am