Vertical Band Watermark On 1958 Qeii Wilding?

Bah. You are both extremely helpful and I appreciate it very much... but I seem to have some kind of mental block here, because this stamp is just not doing what I keep expecting it to do. I have tried it under both long and short waves. The only difference was that the strip down the middle (from the front of the stamp) glowed brighter under the long. No reaction at all from the sides, regardless. And the back simply glowed its pretty phosphorous self at me. No error there that I can detect (which actually means little to nothing, considering...)

Given that I have thousands of wildings, I was hoping to "get" this, but it looks like I'm going to just set the whole bunch aside until I find somebody locally who can look at /explain it.

Thank you for all your patience and thoughts. You've been very kind.

Fluorescence in the paper (optical brighteners, contamination from soaking, etc.) may be overpowering the phosphor reaction. You can try looking for the afterglow from the phosphor bands. In a very dark room,
1) illuminate the stamp under long wave UV,
2) close your eyes for a couple seconds,
3) turn off the lamp,
4) then open your eyes.
The afterglow may be visible for a few seconds. This technique is necessary for identifying some phosphors on Machins.

I just tried this on a mint 1/2d QEII (Scott 353, 1958) with 2 bands and noticed a stronger afterglow with short wave UV. An afterglow was present under long wave too, just not as strong.

Hope this helps,

Robert