In checking the Brunk and Rulau references, I didn't see this combination of letters listed, so as expected, yours is a maverick. Unless it can be matched to say a toolmaker's mark or some patent mark, it'll remain unattributed. Another remote way that such counterstamps can be attributed is that the same mark may show up on another host coin that has additional marks that offer a clue. For example, I have a large cent that reads J.S. DEARBORN, accompanied by a J.S.D counterstamp. Dearborn was a Maine toolmaker and worked as a blacksmith.
Your C.C.W c/s is well-aligned and centered, leaving me to believe that it was applied with a single, prepared punch as opposed to the use of three different, individual punches, being C, W and the period. The letters are neatly designed, not crude, and in the style of those mostly seen in the 1850's. I'd then conclude that the c/s is not simply grafitti as PB suggests but did have some purpose. Of course, that purpose will remain a mystery until the mark can be matched and/or attributed.
Meanwhile, you have an interesting numismatic item. It's been estimated that 10% or more of coins circulating in the mid-1800's were counterstamped. Someday, maybe the
Red Book will give this branch of collecting the attention it deserves.