Hi John,
Thanks for the link to the RTS. This is a delightful variant of the RTS called the RTS Fundus or RTS Scientific or RTS Medical. I love these bodies and have four of them. The main difference between these and the conventional RTS is the presence of the shutter speed lock button on the front of the camera - it stops the shutter dial from moving from the Flash setting without the button being depressed. Most (the ebay one does) but not all also have a raised surround to the actual shutter button that helps to prevent accidental tripping. Some also have d&ed mirrors. Again some but not all (I have variants of all of the above on my cameras) are marked 'Scientific/Medical' on the baseplate. These bodies are slightly heavier than the standard RTS.
Of course, the 137MD had its strange variants in the form of the different CGCM models. So far I have been unable to find any info on the other 10 or 11 (it's alleged that Contax made about a dozen) 139 Scientific bodies that also have d&ed mirrors, the heavy, durable covers that extend to the pentaprism and that unfathomable metal strip on the front plate.
Good night all...