Thanks for the reply! That helped me piece more of this together. I agree on it being 1967 2nd series. It looks the auction I referenced had incorrectly identified it as 1970. It looks like many of the eBay auctions are confusing the 1967 and 1970 wrappers. The 1970 School Daze back-slapper stickers seemed to be more heavily typeset whereas the 1967 were more artistic with freehand printing
In case it helps others, here is where I'm at so far:
1967 1st series wrapper reads "Back-Slapper Stickers" on the front.
1967 2nd series wrapper reads "New Insults Back-Slapper Stickers" on the front
1970 series wrapper reads "School Daze Back-Slapper Stickers" on the front
For 1967 1st series, the US and Canada versions are the same except the US version sticker peels off vertically whereas the Canada version peels off horizontally.
Mine peel off horizontally (Canadian version?) but the stickers themselves are completely different (making them 1967 2nd series?). Also wierd is the stickers are not numbered and there is a blue mystery "dot" placed on the face within the lower quarter of the sticker. It is on each sticker but at slightly different places along that edge from left to right. On my sticker in the post, it shows up underneath the "A" in "Let's Monkey Around". I'm wondering why the artist put these there, or if this was some sort of indexing mark used during the printing and cutting process? Clearly the blue dot is was applied during the printing process. Perhaps an "oops" that got fixed later? I haven't been able to find any online or a checklist to compare to. I'm hoping someone else has some of these and help put that mystery to rest. In the meantime, all I know for sure is I have 51 out of ?? non-duplicates in really nice shape!