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My local used dealer just listed a Pentax S, with a 155XXX serial number. He has excellent photos of the camera, and does mention that the shutter curtains stick halfway when the shutter release is pressed. BIN price is $799.99. His listings are straightforward, no BS, and I've bought many cameras and lenses from him.
I don't have a dog in this one, but I haunt his site every day for great stuff. Thought some collectors might be interested.
:[VERY RARE] Asahi Pentax S 35mm Film SLR Camera Body Only #155627 [EX+++] | eBay