It sounds like some would be most comfortable if we propose a unique design. So I did a little quick analysis on the various key molds. Each existing mold as used on previous clay chips has some similarities, and some differences. I'm not a graphic artist, but I feel like we could come up with a greek key design that is different from all three. First, some photos.
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LGK has no outer ring, and has 15 keys.
MGK has an outer ring, has 22 keys, and uses a simpler key that doesn't hook back downward at the end.
SGK has a wider blank area before getting to the outer ring, uses the same key design as LGK, then also has an inner ring and more blank space before getting to the inlay area.
Personally, SGK is my least favorite.
I like the more complex key used by LGK, and the outer ring of the MGK. But I suspect the more complicated key might be too complex for a Tina mold chip.
Here's the key mold proposed by Justin in the OP. If you will notice, this key mold design has 26 keys. It uses the simplest key, and the outer ring of the MGK, but with a different number of keys. And the inner ring of the SGK. It's sort of a hybrid of MGK and SGK, and technically it is unique, and not an exact copy of any of the other three. Seems to me that we ought to be good to go with this design should we choose to move on Greek Key mold. Clearly the other chip manufacturers in the past felt that changing the design of the key and the number of keys was enough to make their design their own, and not infringe on any previous key mold trademark.
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Great detective work!