[Joe_G.]

I'm not a T206 guy but have studied domestic cigarette taxation. If the stamp is original to the pack, then the pack was likely issued 1918 or later, no earlier than 1917.

12 count was legal on "Class A" cigarette packs . . .
- prior to May 1st 1879
- Nov. 2nd, 1917 to 1945
- 1955 to ?

This particular stamp is considered a "Type III" design which for the 12 count pack likely wasn't adopted until 1918 although still considered a "Series of 1917" tax stamp.

For reference . . .
Legal pack sizes in 1910 were 5, 8, 10, 15, 20, 50, and 100 and would remain unchanged until 1917.
Legal pack sizes in 1917 were 5, 8, 10, 12, 15, 16, 20, 24, 50, & 100 with some change in late 1917/1918 with 16 count eliminated and adding 40 and 80.

I much prefer the simplicity of 19th century cigarette packs where everything from May 1st 1879 on was 10, 20, 50, or 100 (no exceptions unless manufacturer broke the law).