Very unusual brass cased Veterinary spring lancet. Note that the blade retracts back behind the drive spring after firing. The piece is decorated with a nice shell on the end of the release mechanism and on the back plate. It is marked with the makers mark LOB. Probably German in origin c.1800-1825.
The mechanism functions by allowing the raised nib on the drive spring to glide past the blade during loading and the blade to retract after firing is complete.