The Colgan's checklist without projection and minor printing variations is thought to be complete at 289 cards.
I picked up two cards at the National, both picturing Heinie Peitz. The one below is the checklisted version:
I have never seen the second Peitz image (and it is not currently checklisted):
This would be easily resolved if the second image had a reverse. It has been skinned. The paper exhibits the same consistency as other E254's but I cannot be certain that there was ever any printing on the backside. The card has a slightly irregular cut that can be seen in the scan. It also displays some white areas around the periphery (see about 12 and 2). This is not consistent with other E254's as they were punched from a gray background. This one appears to have been cut from a white background.
Some information regarding Peitz. He played catcher for the Reds and Pirates, finishing with the Pirates in 1906. He went to Louisville following 1906 and was there as a player until 1909. He managed Louisville for part of the 1910 season. Peitz was out organized ball in 1911 and 1912 and returned to manage St. Louis in 1913.
E254's were issued from 1909 to 1911. It would be most logical if the uncataloged piece was issued with the gum that it is an E254 and not an an E270 Tin Top which were issued in 1913.
Other possibilities...a discarded proof or prototype, or maybe a piece of an ad (I would expect it to be much thicker and have a different consistency). One last bit of information...Lew Lipset mentions in a footnote in the BB Card Encyclopedia that two different photos exist for Peitz in the E254's.
Opinions and theories welcome.