There isn't anything in or on this pocketbook to indicate an exact date. My ggg-grandfather was born 1829, died 1909. As mentioned before, Colonial Williamsburg has a very similar one, also leather, in their eMuseum, dated ca 1839. So, I think it's safe to say mid to early 19th c. CW also has several others of similar design but of cloth and needlepoint dating to 1770's.
Dimensions:
6-3/4" x 3-1/2" when folded closed
Opened flat 6-3/4" x 8-5/8", not including the closure strap which is 9" long.
Inside pockets are 6-3/4" x 2-3/4"
-Ron