Yashica has been around forever but, at least in the US, never managed to climb out of the 2nd tier of Japanese makes. I knew a few people who owned and loved them, but I could never get excited about them. I don't know why, but to me they lacked a visible identity and character that the others, particularly the Big 5 (Canon, Minolta, Nikon, Olympus and Pentax). Camera magazines used to call some of these "me too" cameras, as in "Nikon has this feature, me too!" May not be fair, but that was always my perception.
This must have been a big seller because made a ton of them, and with variations. The base Electro 35 came out in 1966 and has a cold accessory shoe (no electrical contacts to run a flash), and the ASA dial stopped at 400.
The G version came out in 1968, and they bumped the top ASA 1/3rd stop to 500 (woo hoo). The 1969 GT version was a G with a black body. Both got a "Color-Yashinon" lens; whether they actually changed the optics (like adding a coating) or whether it's solely a marketing gimmick, I don't know.
In 1970 they revised it yet again with GS, which is a G with gold-plated electrical contacts inside, and they bumped the top ASA on the meter to 1000.
The final versions came out in 1973, the GSN and GTN, which were the same as their earlier models but had hot-shoes for dedicated flash.
This was given to me by a friend who loved it. It's a camera I still want to run a roll of film through someday to see for myself what the allure is. Maybe I've really missed out by not using it.
Camera manual: Orphan Cameras.com