Hi Jason,
I know very little about the four different known E121-80 back variations, but I can confirm that I have a WaJo with the Hands-at-Chest pose with a Type 1 back (most common back, I believe) in addition to having this WaJo pose with a Type 4 reversed back that I showed in the thread you mentioned. I'm curious to know if this WaJo pose was also issued with Type 2 and Type 3 backs.
I think Rhett Yeakley is the resident E121-80 back expert, and hopefully, he will chime in. Here's the link to pictures of the 4 different backs that Rhett shows on his web site:
http://www.starsofthediamond.com/e121backs80.JPG
Hope this helps,
Val