DTR is the basic process that enables instant photography as practiced by Polaroid, Kodak, Fuji, 20X24, and was a key step in the development of integral films such as now made by The Impossible Project.
Here is a link to more posts about DTR, which was invented before WWII. And here is a link to the Rott patent. Weyde invented DTR.
Type 55 was just one of many products that depended upon the use of DTR to produce a negative that is processed in such a way as to rapidly produce a transfer of metallic salts onto a receiver, bridged by a developer. The action of DTR is battery-like and DTR kinetics are complex and still being studied today.
I wanted to show some results of DTR that we have produced here. They are early and crude, but show definite ability to use existing films - in this case EFKE 25 - as an emulsion capable of generating a sharp, high tonal gradient DTR image onto suitable receiver paper.
Below is a DTR image produced using EFKE 25, in our own sleeve, and employing 17 year old T55 reagents and paper that was ruined by humidity, which in itself is very instructive. I shot this today in a Speed Graphic with a 545 holder to point out where we need to buy tooling and obtain materials for a new product.