I have been putting my vintage patterns in order by year and maker. I have found some that stumped me for awhile until I knew just what to look for or came up with some solution for them.
Here are two of the sites that I used in dating my patterns.
This one was the most help in dating unmarked envelopes and Mail order patterns.
For anything the first site didn't cover this one helped some by being able to look at patterns that had already been dated.
-Vintage Fashion Library-