Locate the serial number of a Waltham pocketwatch by removing the back to view the movement works on which the serial number is engraved. Take care to distinguish between the case serial number and the movement serial number.
Waltham designed four types of vintage and antique pocketwatch cases: screw-off, snap-off, hinged and swing-out. Screw-off case backs usually rotate counter-clockwise for removal. Snap-off cases include a notch to insert the edge of a specialized tool to remove the case back. A hinged case is similar to a snap-off, but the back attaches with a hinge. Locate the notch at either the 6 o'clock or 9 o'clock position, and open the case back. For a swing-out case, remove the front bezel and crystal, and move the watch crown and stem to the position used to set the pocketwatch before attempting to swing the movement out to locate the serial number.