The 280's (and to a certain extent, even the TLA 20's and 30's) are a system flash, so there's an additional aspect to them that goes beyond the Yashica siblings. You can connect 2 of them together - or multiple units - to act as one massive light source. It does have 2 flash tubes, but they are still a synchronous flash, as they aren't timed independantly. The front tube acts as a fill, while the main/larger tube can be a direct fire, a bounce, or somewhat modified with gels or 'widened' with a snap-in fresnel panel. The 20 is static, with front/direct flash only, and the 30 has a vertically swiveling flash head for bounce, but the 280 is a full swivel type head. The TLA-360 goes one better, with zoom and automated capabilities too.
The 280's (and 360's) are not quite aimed at consumer's doing snapshots on holidays, but they can be an alternative to the RTF 'Hammerhead' flashes for pro users, and can be a lot more versatile when 'wired' flashes will work in someone's workflow. They and the 360 are also the only one of the Contax speedlight-type flashes that uses the additional contacts on the hot shoe when needed for full TTL use with the later bodies that gained that function.
The compatability and manufacturing origins were similar to Zeiss/Contax and Yashica gear. I'm not sure if any TLA flashes were made in Germany, but they were intended to be used with Contax bodies. I'll have to see if they are compatable with Yashica bodies.
Any idea who made these flashes in Japan? I have got to assume it was not Tomioka. Was it Ysshica? It sounds like to sort of thing that a camera/lens manufacturer would out-source. Did Nikon, Canon, Pentax, Minolta, etc. make their own flashes? I assume that, like their lenses, some did and some didn't. And I know that Vivitar didn't make their own (great) flashes, but I don't have a clue as to who did.
I don't have anything that confirms Yashica was the sole manufacturer - but - they did create their own flash systems as part of many of their own point-n-shoot cameras and even SLR's too (like, the 230AF, the Flash-o-Set etc.). They were perfectly capable of engineering electronic components, and I don't see them having any need for outside suppliers, so I doubt there was anyone else making absolutely everything. As biggles3 had noted once upon a time in another thread, the TLA-480 flash model (the upgraded RTF TLA-540) was a rebranded National PE-480sg (i.e., Panasonic's camera flash division), so obviously there's at least one flash that wasn't home grown.
I did make an error in describing the later flashes. The 280 wasn't a full swivel - that was the 360.
On compatability... the early TLA flashes were fully compatable with the concurrent Yashica models (FR, FX, etc.) - but - the addition of TTL in the Contax bodies and flash models may have broken that capability with the TLA-280/360 flashes, and the optional TTL cord and module for the RTF 540. Further info when I can test.
A site or page for C/Y flashes? Not that I've seen, but it's not something I've gone searching for either.
For the most part, there's not much of a mystery on the general characteristics on both brands. The model numbers on the electronic flashes are usually the guide numbers, or the 'number.fraction'. So a Contax TLA-30 is a GN 30, and a TLA-360 is 36.0. I think Yashica flashes follow the same pattern. The Contax 'system' wiring has keyed plugs on the ends, and will only plug in one way... and the hook ups are as logical as using AC extension cords. Other than that, the voltages are all on the lowest end of the scale, and they're mostly 6v or less from what I've measured for the TLA models for Contax, and both the CS and AF models for the Yashicas.
The system wiring aspect for the Contax line was probably the only unique feature either brand had, so everything else was a "me too" feature. The only head-scratcher I've ever had was what camera had secondary curtains, to know which flash head would work with it.
There's no single point of reference that I'm aware of for every single slice of data on Yashica/Contax flashes. That doesn't mean there isn't. If it turns out to be true, where no such page or site exists, I think there are the obvious places to find whatever possible detail one might need... in the user manuals available online, or in user provided 'research' articles, forum posts, or at worst, the Q&A type sites like reddit.
Do a web search for "flash voltage", and you'll find a pretty exhaustive list - on one page. Got to Mike Butkus' manuals site, and find a large list of links for multiple manufacturer's flash manuals - on one page. With a minimum of effort, most of what there is available can be located in very short order. If there's a specific question about what is elusive on the web, there are probably a few here on the forum that may have detailed answers, if asked.
As a good example, the Contax TLA480 and the National PE-480SG look identical; of course, Contax/Kyocera made sure you could not use the National unit by modifying the TLA480's battery connecting cables. If memory serves, the TLA480 cost about £450 for the flash only - if you wanted to fire it, it would cost you another £300 to buy the battery box and cable! The National version came with the battery box and cost around £230.
As an aside, even today, the cost of flashes sold under a camera's brand name are very expensive when compared with like-for-like independent units. One can't help wondering if a degree of price fixing exists for independent manufacturers that have been licensed to make camera-dedicated flashes - did the permission to make and market a Canon, Olympus, Fuji, etc. compatible flash carry with it a minimum price guarantee in order to avoid seriously damaging sales of their branded units? Of course, price-fixing is illegal so it has to be mere coincidence...
Thanks for the info about "National" flashes. I was unaware of them. As "Ponder & Best" and later "Vivitar" -- as well as "Soligor" etc. -- never actually made lenses, I had always assumed that they never made any other accessories either -- such as flashes.
So Vivitar & Soligor flashes may have been made by National or who knows???
I'm almost afraid to ask who are the major electronic flash manufacturers!!!!!!!!!!!