Where is this information coming from?...the One Piece Button became virtually extinct with the advent of the 2 Piece Button in 1813...
I dont know much about vented /blowhole buttons and I dont know if any had 3 holes but here is a thread on those 1700 type buttons. http://www.treasurenet.com/forums/my-best-finds/216095-blowhole-buttons-only-2.htmlThat is an interesting button. Some of those buttons with blow holes in the back are Colonial. I'm not sure if this is one of them but I am sure someone will chime in who knows more
When you enlarge the pictures by clicking on them it actually looks like the button is a three piece one, The front and back look like they are held together by a band. I don't know about others but it looks fairly modern to me.

One last image from Sgt Riker's Civil War Trading Post - Miscellaneous Buttons
Lower right kind of resembles the one I found, except it has 4 marks instead of 3. Thanks for looking.
View attachment 1329068
| [FONT=Arial, Helvetica, sans-serif]1871-1873[/FONT] |