Radiotone process on copper plates

We've been trying to figure out what a "Radiotone" print is over here.

The "print" in question is made on a copper plate about 1/16" thick. Appears to be at least from the turn of the last century. I figured that maybe someone from this forum may be familiar with the process. Nothing comes up on a Google search.

That's a neat looking picture. No idea what it is, though I'm sure that someone here will know.

The use of the word "Radio" in a product name "may" be just capitalizing on the popularity of Radio. I have seen this many times in products from the 1920's, and 1930's, when radio was going great and everyone wanted to be associated with it.

The images posted of this photo appear to be from the 1920's. Making an image on copper plate is not that unusual, although primarily engraving on copper plate was done for making printing plates. It would be only a minor modification of the copper plate engraving process to produce a positive image for viewing. The plate-making process involves exposing a plate with a UV-light sensitive coating, with a negative. The coating is "developed" leaving behind a layer representative of the image, and then the plate is acid-etched to create peaks and valleys in the metal which represent the image. If the valleys were filled with a pigment, then you would have an image such as the one shown in the sample linked thru the discussion linked in the first post.

The image-making process is not very unique. The "name" of the Process, "Radiotone" is probably a trademark of one vendor for this process, rather than a generic name for the process.

I looked around online a bit, and found this:
http://www.sharlot.org/archives/photographs/19th/book/chapter_9.html

It could be a transfer of a silver-gelatin emulsion onto the copper.

Also, this is interesting.
http://www.icom-cc.org/Documents/Wo...rimMeeting/2004/ClaravonWaldthausenPoster.pdf

The PDF makes a brief mention of "the Radiotone photograph". It states that it looked like a half-tone photograph, but XRF (X-Ray Fluoresence) analysis proved otherwise. No more detail is given, but from this I'd assume that its less likely to be a litho print or pigmented etch process.