Here are scans of Scott #294 and #295 from the above issue. The catalog suggests that on-cover with Expo Cancel commands quite a premium over the used values.


Unfortunately, I do not have them on cover nor are they complete cancels ... merely cut squares ... but would these have a premium value over the stamp alone?
Also, Scott Specialized shows an example of a machine cancel which does not show the triangle ... would that suggest that these are the "Expo duplex handstamp" cancel variety (although they don't look like handstamps)?
I'm not quite sure. In any case they will stay on paper. I found three (3) of each denomination ... all with the same on paper cut square that does not show a date, merely with the triangle "Pan American Exposition 1901."