Yashica / Kyocera CS-15

I remembered to look for that specifically in case you asked, and the answer is, yes. The foot section of the flash is shaped differently, but the pad it terminates in - and the metal contact it houses - look identical. Other than that small sliver of hardware, everything else is vastly different.

Flashes aren't exactly tops in my personal knowledge base, so the similarities will likely pass me by without either getting lucky with some obvious clue or by downright stumbling onto the master maker by accident in a visual search. My grasp of manufacturers is limited to the major players of the OEM brands that do their own stuff in-house, but otherwise, a small number of the Vivitar and Metz lines are probably the most familiar to me. There's something I can't put my finger on about the CS-15 that seems off the mark to be a Vivitar... probably the wacky battery cover that sits in such a precarious place with almost no 'grab' to stay in place. I just can't imagine a familiar mid-brand maker producing something like this. But again, I could just as easily be wrong, so... I'll see what there is at the low end at similar specs to find a candidate to match to.

According to the 1980 dealer price sheet, there were 5 flash models sold under the Yashica brand. The CS-10, CS-14, CS-20 Auto, the CS-200 Auto, and the PRO-50DX. That's the newest list I have that covers Yashica OEM flashes.

There is also a further complication that showed up when doing a Google image search for "Yashica CS-15". There are at least 2 different looking models that share the same model number, where each have different layouts on the rear panel and a bottom battery compartment. This one is listed on KEH and is the other example.

Just a quick observation on the CS-15: it's trigger voltage is truly frightening! In fact, the CS-10, 14, 15, 18 & 20 all have trigger voltages that are far higher than any of the other post-1980 Yashica units; they're so extreme that they would fry any digital camera if used directly on one.

Oh, absolutely ... and that's exactly the reason I bought a couple of the isolation type adapters that cut the voltage down to 6v or less. They can also provide another contact pin depending on which brand, so they'd offer a way to link another flash as well, but that's just a bonus.

There might be one downside to using these adapters, where you'd likely end up with manual settings only. I doubt any TTL functionality would be possible with them, but they do offer safe connectivity.

Yeah, there are are few types from a couple of makers. Wein has the SafeSync for up to 400v (the 990-560, at $49 with the added PC Sync socket), and Vello (the HSA-PVU, up to 60v at $35)  and a few others have some budget models. Size-wise they aren't quite as big as an optical flash adapter, but they do add one more small chunk of hardware to stack off the socket.