Original Item: Only One Available. This is a totally inert and empty BATF compliant United States Navy World War Two era Naval Mk 6 Mod 6 Sea Mine that measures 34 inches in diameter. It features original blue Naval paint and stenciled white lettering, though unfortunately the lettering is quite faint. What we can make out reads:

U.S. NAVY BUORD
MINE CASE MK 6 MOD 6
SED NO 1050??
CONTRACT NORD 14512
EMPTY

Spherical antenna type using a K-type pistol, 34 inches (87 cm) in diameter. This mine was designed specifically for the North Sea Mine Barrage of World War I. However, it was still being used operationally as late as 1978. On 17 October 1917, the Secretary of the Navy authorized the construction of 100,000 mines of this type at a cost of $40,000,000 (40 million dollars). By the early summer, these were being produced at a rate of 1,000 a day with a peak of 1,500 being produced in one 24 hour period. In order to support this rate of manufacture, the Navy built its own TNT factory at St. Julien's Creek, Virginia, capable of producing 300,000 lbs. (136,000 kg) of TNT per day.

The Mark 6 was very successful and remained in US inventories until about 1985, making it the USA's longest-lived mine. 1,400 lbs. (635 kg) total, charge of 300 lbs. (136 kg) TNT. Could be moored in waters up to 3,000 feet (914 m) deep. Three safety devices were employed, one a time delay, one a hydrostatic which held a switch open until the mine had sunk several feet underwater and the third to keep the explosive steps open until the mine had reached a considerable depth. Mod 2 was a rising type, Mod 3 had a Mark 9 case with a 100 foot (30 m) lower antenna. Mod 4 had a Mark 6 case with a 50 foot (15 m) lower antenna. All of these had a few Hertz (acid) horns as a backup firing mechanism. Early units used in the North Sea Barrage had reliability problems, with 4 to 8 percent firing shortly after being planted.

Overall condition is very good, we believe it dates from the WWII period but if could have been produced later as these were identically produced for many years before and after the war. It shows some wear from storage, and a few areas of rusting, but overall makes a magnificent display piece.

34" diameter and approximately 80 lbs. NOTE: The pictured orange chocks were used to keep the mine in place for photography, and are not included.

Due to size of the mine it ship truck freight curbside delivery. USA 48 States Delivery only, not available for international shipment.

Mining during World War II

As far as is known, no enemy ship was sunk by the approximately 20,000 mines used in defensive minefields placed in US waters.

US submarines planted a total of 576 Mark 12 mines and 82 Mark 10 mines in 36 fields. Of these, 421 mines planted in 21 of the fields sank 27 ships of about 63,000 tons and damaged 27 more of approximately 120,000 tons. See US Submarine Mining Success for other information.

Avenger and Ventura aircraft could carry a single mine and in 1944 Avengers closed Palau harbor by mining the entrances. They then sank all 32 ships in the harbor with conventional bombs and torpedoes. A total of approximately 100 ships were sunk or badly damaged in the Pacific during the war by mines laid by Navy aircraft.

By 1945, the Army Air Force was devoting considerable resources to the mining role, with 80 to 100 B-29s based at Tinian being used to mine the home waters around Japan. These B-29s could carry seven 2,000 lbs. (907 kg). or twelve 1,000 lbs. (454 kg) mines. "Operation Starvation" started in March 1945 and continued until early August with 4,900 magnetic, 3,500 acoustic, 2,900 pressure and 700 low-frequency mines being laid. These mines sank 294 ships outright, damaged another 137 beyond repair and damaged a further 239 that could be repaired. In cargo tonnage, the total was 1.4 million tons lost or damaged which was about 75% of the shipping available in March 1945.

This long-term mission had five phases: Phase I was aimed at the narrow Shimonoseki Strait between Kyushu and Honshu which was considered one of the most vulnerable points of Japanese inland shipping. This phase also targeted the naval shipping bases of Kure, Sasebo and Hiroshima. Starting on the night of March 27, seven missions by the 313th Bomb Wing laid 2,030 mines, closing the Shimonoseki Strait for two weeks and incidentally forcing the Yamato battle group to exit the Inland Sea through the easily monitored Bungo Strait.

Phase II was intended to block shipping around the Inland Sea and attacked the Shimonoseki Strait again along with the major harbors of Tokyo, Nagoya, Kobe-Osaka and other points inside the Inland Sea. In just two missions, on May 3 and May 5, B-29s laid a total of 1,422 mines, mostly Mark 25 magnetic types and some of the new Mark 25 pressure type which were considered unsweepable.

Phase III was aimed at blocking traffic between the Asian Mainland and Japan by mining the area between the Shimonoseki Strait to Kyushu and Northwest Honshu. 1,313 mines were laid beginning on May 13. By this point, mines were sinking more ships than were submarines with 113 ships sunk in the Shimonoseki Strait alone.

Phase IV saw strengthening of the fields on the western coast of Japan and replenishing existing fields in the Shimonoseki Strait and the Inland Sea. This started on June 7 and went until July 8 with 3,542 mines being laid.

Phase V was intended to initiate a "total blockade" of Japan. This began on July 9 and lasted until the end of the war. 3,746 mines were laid to replenish existing minefields and to extend them to Korean harbors. During all phases, a total of 1,529 missions were flown by the B-29s with only 15 aircraft being lost to all causes, an attrition rate of less than one percent.

Between January and March 1945, B-29s also closed the approaches to Singapore, Saigon and Camranh Bay harbors by magnetic mining.