SEAL Sub Delivery Team One SDVT-1 Mark 11 / MK XI Mini Manned Submarine Blue Version Navy Challenge Coin

This coin is approximately 3 inches in diameter. 

There appears to be 6 different versions of this coin made:

1. Blue, 2. Red, 3. Antique Bronze, 4. Hologram Red, 5. Silver Finish, and 6. Oil Drip

NOTE:  Images have been blacked out to deter fakes being made.

The SEAL Delivery Vehicle (SDV) is a manned submersible and a type of swimmer delivery vehicle used to deliver United States Navy SEALs and their equipment for special operations missions. It is also operated by the Royal Navy's Special Boat Service, which operates three SDVs.

The SDV, which has been in continuous service since 1983, is used primarily for covert or clandestine missions to denied access areas (either held by hostile forces or where military activity would draw notice and objection). It is generally deployed from the Dry Deck Shelter on a specially-modified attack or ballistic missile submarines, although it can also be launched from surface ships or land. It has seen combat in the Gulf War, Iraq War, and the US intervention in Somalia.^[9]

The SDV was intended to be replaced with the Advanced SEAL Delivery System (ASDS), a larger, dry submersible that is often confused with the SDV. The SDV is flooded, and the swimmers ride exposed to the water, breathing from the vehicle's compressed air supply or using their own SCUBA gear, while the ASDS is dry inside and equipped with a full life support and air conditioning system. The ASDS was canceled in 2009 due to cost overruns and the loss of the prototype in a fire.^[10][11] The Navy currently plans to replace the SDV with the Shallow Water Combat Submersible (SWCS), which will be designated the Mark 11 SDV.^[1] The SWCS is expected to enter service in 2019.

(REF: https://en.wikipedia.org/wiki/SEAL_Delivery_Vehicle)