A lot of research has resulted in a plausible theory of why some vintage Rado watches have an E appended to the name or 5-digit reference number (pre-1973). The E is thought to signify that the watch, whose earliest examples were powered by an AS movement, is a newer one powered by ETA (e.g., Diastar 1 and 1/E). Read more about this in the Rado Forum at equationoftime.com.
My new feature article about early Rado chronometer watches has been published
in the Watch & Clock Bulletin of the NAWCC.
Now that it has been issued in print, I’ll also be adding some updates soon and posting it on WatchCarefully.com with additional images and information. For a teaser, check out #rado56h on Instagram. Here are a handful of images to give you a flavor...