Couple of FYIs.
-Colt wrote back and if I pay the $75 they'll tell me what I want to know. I expected that. They did send me a list of reference books and a catalog.
-From one of the Colt Forum members who seems to really know Colt history. I didn't use his forum name because I didn't ask his permission. But if you chose to view go here
http://www.coltforum.com/forums/showthread.php?t=12753&page=2;
"Colt did ship double cylinder Trooper Mark III's but these are rare.
Colt made the Mark III in 22LR and in .22 Magnum versions.
It was simple for Colt to simply fit an extra cylinder for a convertible gun.
I "think" (note the qualifier) that these two cylinder guns were a limited production item, not a special order by an individual.
I've seen these in two forms. One is simply a loose cylinder in the box.
In order to install it, you have to unscrew the ejector rod and slip the cylinder off, then install the other cylinder and install the rod.
I've also seen a couple of guns that had a complete extra cylinder AND crane assembly.
All you had to do there was remove the cylinder retention screw and plunger and slip the entire unit off and the other unit on.
This is the way most companies made special order double cylinder guns, because it was easier to make the switch and less chance of damaging the cylinder assembly than having to disassemble it."
-I got this from SAAMI.
http://www.saami.org/specifications_.../publications/
.22 short to .22LR bullet dia. = .2255; case dia. = .226
.22 wmr bullet dia = .2245; case dia. = .242
This, except for case dia., is opposite to what every one has been saying. I must be missing something.