Quoted:
I don't know a thing about subs, but I can tell you about the third world procurement process.
It was cheap, looked good, and was available.
I might go with that, in a way.
The Gatos, it seems, didn't start getting transferred to foreign navies, most of them European, Asia Minor, till the mid 60's. The Barb was transferred to Italy in the mid 50's but that may have been a special deal, perhaps a compensation, and in any event, Italy's standing was probably better than Peru's. Speculating, mind you.
The Mackerel design might not have quite available, but I can picture it like this, "You won't let us have a Gato, how about if we bought a few boats of an older design?". Perhaps not the kind of talk of customer and builder but one that diplomats might come up with.
Now, a French Narval design might, historically seem the better choice, but a few things. While similar in size, that was probably one of the more advanced diesels at the time, some calling it a follow on design to a XXI U-Boat. Ie,
and a Narval
The US might not have been willing to sell a Tang but the French are more mercantile, so maybe. But two things, there would be the cost and the parts issue. Perhaps it was more likely to find parts for a near WWII design than something new. As another comparison to then, it was a time when Mk 14 torpedoes were standard, Mk 37's were high tech, and Mk 48's were a dream.
When I first came across the Abtao's, I, too, confused them for the training SST's of the 50's. At the time, I believe I was writing trivia questions for midshipmen......such is the life of an 1100. They always fascinated me because as stated, they appeared to be the last export diesels that the US allowed for a foreign country. In recent years, however, the SST's have shown up in literature, both about NR-1 and in a pocket book that sits by the john, so I decided to look up the Abtao's again............and the specs, the pictures did not make sense.
This is not, modified or not, an SST submarine.
Thank you for the input!
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("This is not your father's oldsmobile!"––voiceover, (w,stte), "Oldsmobile commercial")