Ian T. located the following information - ORDNANCE DEPARTMENT LEAD SEAL HAND PRESS – RARE EARLY TO MID 20TH CENTURY INSPECTOR’S TOOL - MC Pheeters Antique Militaria "this United Seal Company hand operated Hot Press Tool was used for clinching lead security seals that were placed on packing crates and containers to prevent tampering and theft. Each of the jaws is fitted with an emblem discs to emboss the lead disc on the seal - one having 'U.S.' and the other has the Flaming Bomb insignia of the U.S. Army Ordnance Department." See link for images.