It's been about 6 months since we made an addition to the written checklist. I saw a post on the ever interesting Vintage Non-Sport card forum written by our good friend Lonnie Cummins that referenced a Valentine version of Topps Nasty Notes (1967) that was issued in early 1968. Topps added a "valentine" sticker to the Nasty Notes box but used the same pack wrapper. I believe that there isn't a way to distinguish the two packs except by opening them (horrors!)
Click the first box to go to the forum post
Click the second box to go to a good discussion of the various Topps Valentine issues