T5 Pinkerton mystery cards

[T206Jim]

Ok, I'll take a stab at quantifying what I'll tentatively dub the "1911 T5 Pinkerton White Borders" variant.
1. The cards are 3 5/8 x 6 inches in size, larger than other variants.
2. They are real photo cards.
3. They are on cardboard stock similar to a postcard.
4. They have much larger white borders than the T5 cabinet photos or the blank back/scorecad backs.
5. The were printed in 1911,(T5s issued in 1911 and Leon's Baker postmark).
6. The set to date consists solely of Philadelphia Athletics players.
7. There are five known examples; Baker, Bender, Hartsel, Morgan & Oldring.
8. They have blank backs.
9. Speculation it may have been issued in to commemorate the 1910 or 1911 World Championship and perhaps in the Pennsylvania region given the postmark.

If this is truly a recently discovered Pinkerton variant it appears to be far more rare than any of the other Pinkerton variants. Can anyone add to contradict the theory posited above?