More Questions With My New UV Light (Used US Stamps)

This stamp is listed in Scott as not tagged. My stamp appears to be tagged, though it glows differently than other tagged stamp, it is clearly different than other copies of the same stamp:



this one has an odd spot that is not visible in daylight:



this group looks like the tagging was washed off (is that possible?)



same group in normal light

Alub, I like to specialize in the Transportation Coils. I can help with the 16.7 cent Popcorn Wagon. The stamp is a precancel and as such is not tagged. What you see is the addition of brighteners to the paper on the left stamp. Some papermills used brightener in their paper to make the stamp look brighter, or whiter.
Depending on your UV lamp's wavelength you can see these brighteners as if it was tagging.


Peter

The other two just a guess. The 4 cent is most likely just a fluke - maybe the edge of the tagging mat ?
The strip of 22 centers is most likely just a lack of taggant; as far as I know the taggant does not come off of these stamps


Peter