A very early original portrait miniature, I'd say late 1600s to early 1700s from fashion and clothing, hair, beard style, and the fact he is painted in oil on a copper plaque, consistent with the early portraits. These paintings are more stable than those on thin natural wafer which are subject to hairlines, paint loss. This one has a newer frame so was likely in a shagreen case originally. Those seldom stood the test of time and many were discarded with the painting framed again later. The frame is bespoke, very nicely crafted, and is early to mid 1800s. There is a cover glass, though when painted, this type of portrait would not have been under glass and really needn't be. Full measurements appear on the Photos.
Very good to excellent condition for age and type, the painting is thrilling - early! Very little loss to it as it is oil painting on copper plaque, very sturdy. As noted above, the frame is newer and made specifically for this early painting. It will display beautifully and is itself a fine antique from early to mid-1800s. Found in France.