Good find Patrick. I have a GSN too.
I litterally found my GSN in the trash. Looked ok except for a dent in the filter thread and no battery. I found YashicaGuys site and then found a battery for it. I was totally shocked when this thing powered up and took pretty good photos.
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Collector and avid user of classic and vintage cameras: Yashica Electro 35 GSN, Zorki-4, Neoka 35 IVS, Mamiya 35S2, Voigtlander Vito CLR, Ricoh 500GX, Minolta A5, Ensign Commando MF Rangefinder. PLus an assortment of MF, Zone Focus and SLR cameras.