Identify a mark

[RDSEVERN]

HI, The mark on this necklace is a soccer ball with 925 MEXICO encircling it and then something that is too faint to read, possibly a letter then C O and then one more letter I think but it's faint so cannot be sure. Any ideas on what the maker's mark might be? Any help would be greatly appreciated. It's a nicely made necklace possibly 1940's - 1950's. Thank you, Darlene