Updated 11 May 2009

6" (15.2 cm) gun salvaged from USS Maine after she was sunk at Havana in 1898.  Note the inclined hydraulic recoil cylinder, indicating that the weight of the gun itself helped to return it to battery.  This is a "barbette" mount, probably a Mark 3 or Mark 4.
USN Photograph taken in 1975 of display at the Washington Navy Yard

USS Boston in 1888
6"/30 (15.2 cm) gun on Mark 2 Mounting
Note the geared track and the 6" (15.2 cm) projectile
U.S. Naval Historical Center Photograph # NH 56535

6" (15.2 cm) gun on USS Newark (C-1)
An inclined-recoil mounting, possibly Mark 3 Central Pivot
Detroit Publishing Company Collection Photograph
Library of Congress Photograph ID LC-D4-20655

6"/35 (15.2 cm) gun (?) on Second-Class Battleship Texas
In the foreground is a Spanish mine removed from Guantanamo Bay
Detroit Publishing Company Collection Photograph
Library of Congress Photograph ID LC-D4-21019

Crewman "Frenchy" and 6"/30 (15.2 cm) gun on USS San Francisco (C-5) about 1898
Note the quick-release carrying yoke for the projectile and the rammers
Detroit Publishing Company Collection Photograph
Library of Congress Photograph ID LC-D4-20942

6" (15.2 cm) gun aboard USS Powatan ID # 3013
Note the breech mechanism
U.S. Naval Historical Center Photograph # NH 106351

6"/30 (15.2 cm) gun formerly on USS Concord PG-3
Photograph copyrighted by Dana Payne and used here by permission of Woodland Park Zoo

6"/30 (15.2 cm) gun formerly on USS Concord PG-3
Photograph copyrighted by Dana Payne and used here by permission of Woodland Park Zoo

6" (15.2 cm) gun on  USS Susquehanna (ID # 3016) circa 1916
Mark 6 or Mark 7 Pedestal Mounting
U.S. Naval Historical Center Photograph # NH 42089

6" (15.2 cm) gun aboard USS Santa Paula (ID 1590) circa 1919
U.S. Naval Historical Center Photograph # NH 103315

25 December 2008 - Benchmark
11 May 2009 - Added picture of USS Powatan