Late 18th century English ivory set - Calvert?

A delightful very old small ivory set (kings just over 2.3") - possibly by Calvert, as the knights are very similar in carving to a wooden set I have, which a couple of experienced collectors attribute to Calvert (no hard evidence other than "gut" instinct based on the style of knights).

Stand out pieces in this set are the knights and what I will call the "christmas tree" rooks.  I have seen similar rooks in the Rochford collection - which the Rochfords estimate is from 1750.  The Rochford's rooks do not have the pedestal, and have a cruder end to the cone finial, but the main body, battlements and cone finial are very similar.  Given the potential link to John Calvert, and the more refined nature of the rooks, I would place this set at the end of the 18th century, circa 1790-1800.