The frame is original, and typical for this time period.

The original frame is exemplary of a late 18th century gold leaf portrait frame with “a triple reeded top molding with cross straps occurring at 12” intervals, a plain deep cove, a bead and flat liner” .
Description in quotes is from R. Reynolds in a report on the frame of the G.S. Lansdowne portrait on file 1985; I use it because I couldn't describe this any better in my own words!