Many thanks to Colosseum for allowing me the pleasure of sharing these with you here in this thread.
This is SPOT (SS-413) at Mare Island Naval Yard in on 22 September 1944, before her shakedown period. She is camouflaged in Measure 32/3SS-B - the submarine light grey system with black pressure hull.
SPOT shows SD and SJ search radars on masts aft of the periscope shears. The SD mast is adjacent to the structure and there's a whip antenna attached to it. Her bow planes are rigged downwards, not an uncommon modification but noteworthy for being present on a boat just being delivered. There is a single 40mm Bofors Mark 3 mount on the cigarette deck and a single 20mm Oerlikon ahead of the fairwater. A 5"/25 deck gun is fitted aft.
She completed four war patrols and survived the war to be decomissioned at her home yard of Mare Island. SPOT was towed to Pearl Harbor in January of 1961 for modernization in preparation for transfer to Chile.
This is SPRINGER (SS-414), another Mare Island boat, before comissioning on 18 October 1944. She too is camouflaged in Measure 32/3SS-B, the submarine light grey system. She carries SD and SJ-1 search radars, her SD mast being removed from the sail structure. She too carries a Mark 3 Bofors on the cigarette deck, a single Oerlikon ahead of fairweather and a 5"/25 deck gun aft. Contrary to SPOT, her diving planes remain on the stock position.
SPRINGER completed three war patrols and was attached to the Pacific Reserve Fleet at Mare Island on 1945. In January 1947 she was decomissioned. In April 1960 SPRINGER was moved to San Francisco Naval Shipyard to be modernized in preparation for her transfer to Chile.
THOMSON (SS-20), ex SPRINGER was comissioned on 23 January 1961 on the Chilean Navy, transferred from the USN, but only struck from the US Navy list and sold to Chile on 1 September 1972. She was decomissioned and sold for scrap in 1981, even though she hadn't been fully operational since 1973.
According to Augusto Zimmerman, press secretary for Peruvian president Juan Velasco, in 1971 a submarine was detected near the port of Ilo and depth charged by destroyer VILLAR (ex-Benham DD-796), though the submarine evacuated the area succesfully while submerged. THOMPSON spent time inoperative and in reduced comission until about 1977 and then quickly sold for scrap, which leads me to believe that this was the unit that starred in this incident.
SIMPSON (SS-21) ex SPOT as arrived at Chile on 23 April 1962, after being transferred under MAP. She was outright sold and struck from the Naval Register on 1 August 1975.
At some point in the 1960s she received a sail like THOMSON, and in 1978 featured as the only available Chilean submarine during the Beagle Channel crisis. Under Captain Ruben Scheihing, who was authorized to commence hostilities against any targets that approached the channel islands, SIMPSON stood alone and in the dark against the advancing FloMar (Argentine Fleet) with the Captain's promise to the crew that if they went down they'd take at least two with them. Alas, Argentine units reported contacts with a Chilean submarine, one Argentine sub commencing evasive action due to a torpedo report, but SIMPSON's crew never reported contact with the enemy before the invasion was called off. It seems tragicomical to my young perspective to have had two warfleets at the edge of combat nearing the 1980's using nothing but refurbished World War 2 materiel and brave, commited crews to fulfill their objectives.
As far as I have read, these boats did not receive any of the modifications comprised under the GUPPY programs, and I have found no indications of snorkels either.
On a happier turn of events, SIMPSON and tender PILOTO PARDO were extensively used and featured by director Kinji Fukasaku in the disaster film Fukkatsu no hi (titled in English as "Virus" and "Day of Resurrection"), which displays incredible footage of both vessels sailing in antarctic waters.
She was disposed of on 19 of April of 1982 and sold to a businessman who wanted to turn her into a nightclub, but while being towed, a storm cut her tow line and she was grounded on the Lebu river mouth. She was salvaged and towed out by URIBE (APD-29). Then she was towed by a tug to Puerto Montt to be scrapped, but another storm forced the tug to cut the line, whenceforth SIMPSON went adrift and eventually sank, putting an end to a rather colorful carreer.