My new used Pedulla Rapture has a great feeling action, but the previous owner didn't change the strings, and doesn't know what is on it. I would like to find out so I can replace them with the same strings or ones enough like it that I won't have to monkey with the truss rod. Can anybody help me narrow it down? What I can see: Roundwound, soft feel, probably nickel red wrapping Is there something inexpensive that I can buy to measure string gauge? Then I could at least replace the strings with equivalent gauge strings.