There could be "The Excellency Series" and "The Diamond Excellency Series". Two different names for two different groups? Unless we are assuming the latter is a subset of the former. The ad above states "The Diamond Excellency". After rereading some previous threads, no one has made any statement about jewel count in "The Diamond Excellency" or about the Diamond Excellency model variants "C" or "G". They are a new model as of this ad.
Subject watch next to snippet from 1967 ad in root record.
Looks like the "C" to me
...unless we have an ad on site which suggests this dial/case/jewel count could be confused with another model or variant (or other conflicting info like crystal specs, etc). Regardless, the name Diamond Excellency has to be added to the watch database dropdown menu (and ad menu) by Stephen - if warranted.