I'm not quite sure what you mean by this question. Vamworld lists both varieties being discovered in 1974 by the same person, Leonard Hinckley. So there would be no time in which either variety existed singularly.
Oops, I followed sensiblesal's link above not realizing it is a link to 1881-o morgans, not 1880-o morgans. Here is the correct date's link: http://www.vamworld.com/wiki/1880-O_VAMs /ignore my above comment as that pertains to the wrong date. I think those dead links to discussions in vamworld descriptions used to have more information pertaining to your question.
There was a big mess surrounding the 80-O VAM 6 stuff about 10-15 years ago that caused a bunch of listings to become screwed up. The current designations are correct. The ANACS label from above is right after ANA sold ANACS to Amos Hobby in the late 1980s.