Robert's site has this info...

"C" MOLD -- a large embossed "C." (I filled the incused spaces with soap for photography purposes.) H. C. Evans and Co., Chicago IL. c. 1900 to 1930's. (The embossed "C" mold chip appears in a c.1900 Harris Co. catalog and a 1909 Evans catalog. The most recent Evans catalog I found with the mold is a 1929 one.) The Evans catalog proclaims that "the large Casino C is an exclusive Evans' design.." The Harris Co., Brooklyn NY, catalog said the "C" was for "club." It proclaimed that the chip gives a club a "distinctive poker check which cannot be duplicated by any other manufacturer, and will prevent ringers." Jim Blanchard says H. E. Mason & Co. once owned the mold..

So the time frame is right for both places. The Florida Plantation was running before Lansky and Alo got a hold of it.