When was my radio made?
I will be bold enough to suggest that it's best not to fully trust the dates given for early Japanese transistor radios in the price and product guides that have been published previously. Don't get me wrong, the people who have made these references available managed to be accurate on a good percentage of the models and have done a great job overall at disseminating radio info. At the same time, they often had little data to work with in this relatively young field of collecting. And surely they must have been forced to rely on much information from friends and fellow collectors, just as any of us would. Let's face it, preparing all the data for a detailed and accurate book on hundreds of models by dozens of makers would be a nearly impossible task for anybody to date. The valuable foundation these guides have built does however give the community an opportunity to share knowledge and bring together the documented histories in hopes that we may in the near future be able to come up with a remarkably accurate view.
Along the same lines, note that the timing of a radio's appearance in Sams Photofact® transistor radio series is by no means an accurate indication of when the model was launched into the market. There are many examples where a radio first appears long after it went into production, or an earlier model appears later than its successor, and so on. And sadly, many of the early Japanese radios were never included in Sams. (A good number of these early Japanese models were never sold in the States, so it's no surprise they didn't appear!)
I hope to help clarify the dating and other historical data on a number of early Japanese transistor radios. What makes this possible is that I live in Japan, read the language, am blessed with a number of knowledgeable local cronies, and have been spending a lot of time and the other stuff it takes to gather solid documentation only available locally.
Note: Where necessary, I have supplied corrected release dates for models that appear on this site, and I will continue to do so.
So, how can I date my radio then?
While there are several handy ways to determine the date a certain (individual) radio was built based on parts and other clues found inside, and even on serial numbers in the case of one or two makers, the only way to confirm when the *model* went on sale is to find irrefutable documentation on the launch date. Such documentation includes press releases from the maker, new product announcements in period magazines, original sales and service guides released by the maker, etc. I am convinced that one day the transistor radio collecting community will be able to locate enough of these to put together a guide that we can all trust.
Another issue concerning dates
There is one other matter I think it will be important for the collecting community to address in the future. In many cases, one date does not properly apply as an adequate measure of a given model's characteristics or place in radio history. This issue is particularly important for those interested in collecting early transistor radios made up until, say, 1958. The transistors themselves, other components, circuit boards, and the production process evolved quickly during the first few years. As a result, many models of radio differ greatly depending whether they were built near the beginning or the end of the production cycle. The length of the product life also becomes a factor here. I know there are a good number of collectors who do care to know these details and, at least in the case of two American models, the differences have been documented. The two models I speak of are the Regency TR-1 (1) and the Zenith Royal 500 (2). At the same time, I have seen no attempt to document the differences in the early history of Japanese transistor radios. In fact, there are a great number of collectors who tend to think if a radio has a certain "face", or appearance, then that is enough explanation of the model.
Let me use the Sony TR-72 as a quick example while saving the details for future coverage on the model. Sony* released the TR-72 in December 1955, a mere four months after the company's first transistor radio went on sale, and production continued for over four years. This is a particularly long span for any early model and covers the entire period that transistor radio production and the industry in general evolved quickly out of its infant state. Sony implemented loads of design changes as production went on, and the early units differ quite a bit from the later ones. The transistors range from the earliest oval ones that were hand-assembled, hand-tested and sorted for use through 1956 and into early 1957, through the later ovals that reached mass-production in the second half of 1957, to the cylindrical transistors that the company was making in large quantities by 1958. The circuit board also underwent major revisions and was completely changed at the end of 1957. Even the material used for the wooden cabinet, (and the cabinet maker), was changed three times during the years of production. I once answered an inquiry about the TR-72 from a veteran collector in which I divided the value on a 4-tier scale depending on the period of production. It's hard to express my astonishment when I received a reply stating the collector's opinion that, "as long as it looks like a TR-72, then I am not really concerned about other details." This drove the point home once again that many people collect radios as objet d'art or period pieces, and aren't particularly concerned with anything beyond the face. That's fine as these folks still appreciate their radios as much as any other collector, and, as they say, to each his/her own. At the same time, I believe if collecting early transistors is to reach a truly mature state, the details should be made clear and evaluation made accordingly. This is the norm in more established forms of collecting. Back to the TR-72. Personally, I'm kind of tired of seeing every one that appears on 'net auctions described as being from 1956 just because that's the only date that shows in Bunis 2 (3). Many of these units were built as late as 1959, or 1960, and even those from early '58 are already a world apart from the earliest ones.
* Sony Corp. was originally known as Tokyo Telecommunications, Ltd., or "Totsuko" for short. In January 1958, the company adopted the Sony name, which was first introduced in 1955 as a brand name for their transistor radios. On a related note, TR-72 units built prior to the end of 1957 are technically made by Totsuko, while those produced afterward carry the Sony Corp. name. Not one of the major differences found in different generations of the model, but one that some collectors do care about.
(1) For further reading on the history of the TR-1, I recommend Eric Wrobbel's booklet, "The Regency TR-1 Family". You might also want to check out Steve Reyer's highly informative and well researched page dedicated to the TR-1. There are other good sites with TR-1 information as well; you can find these listed on Aldo Andreani's comprehensive list of links, "The Transistor Radio Directory".
(2) There are a few books that will provide further reading on the history of Zenith radios. Norm Smith's "Zenith Transistor Radios: Evolution of a Classic" is just one example, (Schiffer Publishing, Ltd.; ISBN: 0764300156).
(3) Collector's Guide to Transistor Radios, Second Edition, by Marty & Sue Bunis. (1996, Collector Books; ISBN: 0891457046)