Only 4 of these unique vessels were ever built. They were originally planned as LSM's but were never built. Gypsy (ARS(D) 1) was built from what was originally planned to be the LSM-549 hull, Mender from the 550, Salvager from the 551and Windlass from the 552.  The bow of the vessel is unique and  gives it the capability of lifting salvage equipment, etc., from the ocean and harbor bottom. Later, before going out of service, we were told that some of these vessels had their engines removed and had to be towed or pushed to their salvage assignments.