The Brown Internationals (what I am calling Type A1 and A2) were the flagship of Scott's worldwide album line for some seventy years. Even so, Scott had long been aware of the need for an intermediary album that went beyond their beginner albums.
Scott's first attempt to fill this niche was an Abridged International published in 1897. I have no other information about this album beyond that it apparently was not successful.
In 1914 Scott released the Junior International Album which was able to shoehorn the world into one volume by omitting what the editor considered "rare and high-priced stamps." Scott released new versions every year or two for almost forty years. Until the late 1930s there were no supplements so each new edition superseded the previous ones. The initial versions were hardbound, although there were usually several options on type of binding. Editions are often found with a blue binding, hence the "Blue Internationals" sobriquet.
I had originally planned on providing a detailed list of editions, but as I've posted this elsewhere, I think that what might be most useful at this point is a series of summary statements:
--The editions between 1914 and 1943 are named Junior Internationals and largely differ from each other by adding the latest new issues. They are mostly hardbound although Scott started issuing annual supplements around 1938 to get collectors to 1940 without having to buy a new album.
--The 1947 was the first edition which dropped Junior from the title; it is otherwise identical to the 1943 edition.
--The 1955, 1964 and 1969 editions eliminated hundreds of stamps and even some countries that had been in the album but also added some stamps not in previous editions.
--The 1979, 1985, and 1991 editions were published in two parts; these dropped even more countries and stamps that had been in previous editions (although again there are a few stamps that appear in these editions for the first time)
--1994. I have not seen this edition so I do not know if it was in two or four parts.
--The 1997 edition was split into four parts and is the one available today from Scott/Amos Publishing. This edition brought back many of the stamps dropped by the two part versions although there are still hundreds of stamps missing that were in the 1969 and earlier editions. Every country and almost all subgroups of issues (e.g., semipostals or airmails) begin on the front of a page to allow easy integration with International volumes 2 and beyond. The quality of reproduction is inferior to earlier editions but the paper is heavier and of archival quality.
I also want to emphasize what is probably the biggest point of confusion for persons coming to the Internationals for the first time. The splitting of the Volume 1 into two and now four parts was a move by Scott to cover increased printing costs or increase their profits or both. It does not mean that they were more comprehensive.
Although not apparent from the above, there were years at a time when Scott allowed various International volumes to go out-of-print. Scott is now using on-demand printing technology which hopefully means the Volume 1 will always be available for purchase, although you might have to wait while your copy is reprinted.
In the future, I will do a post on considerations in choosing an International edition for your collection.