This is a most unusual early to mid 1800s letter opener. Probably originating from Wales having features similar to the Welsh lovespoons. The handle is finely chip carved, shaped with two open lanterns, each containing a moving ball, (the number of balls on a lovespoon is suppose to represent how many children the suitor would like). So maybe it was made as a love token.
The letter opener measures approx 23cm l x 1.5cm w for the bottom section.