While researching a similar hallmark, I came across an article that identified "er" as being the trademark used by Ernest Rubinstein of New York since 1957. This info won't help much if your ring is actually from the art deco period. However, if the ring is a retro deco style, then this could possibly be the company that made your ring.
Rating
More Information Requested by: Anonymous
Hi - to research this mark further we need clear images. One image of the actual mark. The second image of the mark and the surrounding area, and a third image of the entire item.
Could you provide more information that might help us in focusing our research to a particular period or region? Any other information you may have already discovered and any other details that will help.
The letters PLAT for Platinum is visible. Platinum is a heavy dense hard white metal. It wasn't until the late 1800's that a new torch was invented which provided jewelers the required degree of heat necessary to work with this metal. Platinum continued to be popular through-out the 1930s.
