It's hard to say for sure. Well, it is for me anyway but I think Scott/Amos increased the weight of the pages and darkened the color from "too white" (in my opinion) to "fairly pleasant yellow-white" some time in the 1990s. The increase in paper thickness was necessary because the earlier pages just did not hold up with use, and the holes tore repeatedly. The new weight of pages is significantly better in that regard. I also like the new color much better, personally.
The copyright dates would be a good guide to when this happened.
I'd also contact Amos Media (Scott Publishing) and just ask them. They have people trained to know things, unlike the usual phone answerers who just take orders but otherwise don't have a clue about the products they sell. Just tell the person who answers that you'd like to get in touch with someone knowledgeable about the International pages, etc. and they'll either give you someone's e-mail address or a phone number.
There is also a blog/forum called "Filling Spaces" which has had at one time or other some fairly detailed discussions of the history of the Scott International album and how it's evolved over the years, including recently. There may be a way to 'search' for these threads on that website -- or email the person in charge (blogmaster? forum-master?) who is very nice.
http://globalstamps.blogspot.comOne small complication was the Scott/Amos continued to sell their older International pages for some years until they ran out -- even after they made the changeover. So knowing what year pages were sold is not a reliable guide to which pages you're getting. Often on
ebay (and this happened to me), it used to be possible to buy new/unused pages still in their shrink wrap which were sold not too many years ago, and just never used, so you thought they must be the newer pages -- but they weren't. Scott/Amos may have still been selling older pages at a fairly late date, still trying to get rid of old stock. Or another seller of Scott products might have been selling "new" old stock pages still in shrink wrap. Even today I still see new International pages on
ebay that appear to be old stock, thinner, whiter pages -- and again, knowing their copyright date (or do the pages show a printing date--not sure?) may be a guide to which pages they are. I'd always ask the seller to confirm this -- if it matters to you. Some bargain hunters may not care. I do care because I want my albums to look consistent. A mixture of thin and thick, white and yellow pages looks very strange to me. Also, it seems to me that the older pages were a very small amount narrower (or was it shorter? can't recall for sure) -- but I could be wrong. In any case. older pages among newer pages will look different in your album. They are not the exact same size by a small margin of width, along with the different paper weight and color, as I've said.
Good luck