Sorry to say I have been unable to pin down the manufacturer who used this mark. Here's a clearer picture in case someone else knows.
There is a theory, not mine, that the letter that appears to be a C might be a G. A company called Tilden-Thurber used a crest with lions on each side mark, but without the letters.
When the Tilden-Thurber Company, Providence Rhode Island, opened their doors in 1856 the sign above the window said "Gorham Co. and Brown". Gorham Thurber was one of the officers of the company. Gorham Thurber had also formed a partnership with John Gorham (1850-1852) called Gorham & Thurber. This was a predecessor of the Gorham Manufacturing Company.
Dorothy Rainwater's book states "Working with the Gorham Manufacturing Company, Tilden-Thurber furnished a complete sterling silver service for the Battleship Rhode Island, later placed on display in the State House. They also furnished the silver service for the Crusier Providence, later exhibited at Brown University." So, apparently, Thurber And Gorham maintained close ties into the mid 20th century.
Just an interesting footnote. I saw a picture of this same mark on the presentation silver pieces of the ship USS Wilkes-Barre.
Regards,
Pat.