crossed keys hallmark

Hello,
I found this old serving spoon with a few pieces from Germany and Switzerland but can’t identify it’s hallmark. The marks are on the front of the handle. I am thinking that it is a Continental piece from the 18th Century but of course am unsure. Any help from you experts would be very much appreciated!
Thank you!
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In the “Encyclopedia of American Silver Manufacturers” by Dorothy Rainwater, et al., page 125 has a mark that looks like this; except it is upside down compared to your photo!:

“C. F. Kees and Co. Newark New Jersey. Successor , before 1904, to Henry I. Leibe Mfg. Co. and suceeded by Archibald, Klement Co. c. 1909. They were manufacturers of sterling silver and gold lorgnettes and related items.”