Cemetarian, thanks for the fantastic resource, which I also use often!
For late 60s/early 70s Vogues, there is some pretty useful dating information on the vintage pattern wiki (
http://vintagepatterns.wikia.com/wiki/Main_Page). If you browse listings with numbering close to that of the pattern you're researching, you'll often find someone's entered the exact magazine issue for your rough numbering range...
I believe the 1970s start with Vogue 2263.
Hope this helps!