i have a silver pocket watch with an unknown makers mark i have looked all over the web the marks are JR. i already know that it is Birmingham because of the anchor also the lion and date letter M
A good possibility is John Rotherham. Used a JR mark in a rectangle and diamond shape cartouches. Also used a R&S mark for Rotherham & Sons during this period. In 1917 they started using the R&S in a diamond mark exclusively.