It is not as easy as that. Technically by definition, PLAIN MOLD WITH INLAY, the chip you show is a C&S, but it is what I would call a modern crest & seal and they are still being made for use in Europe by B&G if I remember right. To the purest, a Crest & Seal is a plain mold chip with an inlay that is covered by a clear celuloid cover. By this definition the chip has to antique to qualify. This process was only used up until somewhere around 1945+-. However, you mentioned a rectangle mold and I assume you are referring to a HUB mold with inlay. Chip makers in the 20s & 30s+- (USPCC & BURT) called all chips with an inlay Crest & Seal. So by that definition, all the chips in this picture are Crest & Seal including the the HUB, Small Key, & Machined chip in the botton row. Does that help? Nice meeting you in Vegas Wes.