According to you guys, I gather this: Yes, it's an OD. And yes, it's a 4-speed.
Any other opinions? We need a tie-breaker here. Does anyone have a picture of the inside of a 4-speed? If I am going to dump this one and want to find another, it'd be good to know what I'm looking for. I'm surprised the stamped numbers on the thing give no indication.
As to my assessment of the synchros: My limited experience is based on a '57 MGA I rescued from a barnyard almost 40 years ago. In the three transmissions I had to choose from you could definitively see whether or not the synchros were worn. I chose the best one based on the lack of wear on the synchros and the opinion of a transmission expert. Just one more thing to add to the Gotta Learn More About That List.
As to the counter-balance shaft being out of place: The hits just keep on spinnin'. To answer my Question #9 in the first post, it's beginning to look more and more like "boat anchor" is the right answer.
Now I just have to get a boat.