Name: Cnt. Benjamin Whitney
Location: Sherborn, MA
Date: 1718
Carver: Nathaniel Emmes

The cornet was the position of sub-lieutenant in the military prior to 1815, when it (and the similar rank of "ensign") were abolished.
My abbreviation is approximate here. I can't find any source on what the official abbreviation of "cornet" was.
(For the record, "ensign" was abbreviated "Ens.")