Without a box and papaerwork, a Liberty, Miss. box is worth whatever someone will give you for it. A box usually doubles the value of most collectibles, again, value is determined by condition, rarity and desirability. The most desirable Lynch calls are those made in Alabama, Birmingham or earlier Homewood versions.
The Mississipi made versions, are good hunting calls, and I know of quite a few gobblers who succumbed to the calls from one in particular.
I woud guess it's value at $25-$40, without seeing a picture, if it is an earlier version it will have tuning holes on the striker, generally screw eyes will be silver rather than black