Tagging On Airmail Stamps

I am puzzled by certain things related to tagging. As an example, Scott No. C72, 10c carmine is listed both in a tagged and untagged version. I have hundreds of copies of this stamp and none of them, to my eye, appear tagged using a 254 nanometer (i.e. short wave) UV lamp. The note beneath C72 in the Scott specialized says that the tagging is red. None of my stamps display that color or any other color for that matter, including green. They just look like they are being illuminated by a bright light. I can make these identical comments for C73 through C90, which is as far as I've gotten in my frustration: NOTHING looks tagged, either red or green. Can someone help me out here? Perhaps post a photo of what a tagged stamp actually looks like under UV light?

Check out the Stampsmarter tagging database. It has images of al US stamps to 2019, if I last remember, including back of book.

https://stampsmarter.org/features/TaggingView.html

Use the search by catalog number to find ones you are looking. I took most of the pictures. So feel free to ask questions. Are you using the right type of light?

You should use 254nm light
Here's a quick comparison under short-wave uv:


/added corrected for wrong wavelength

? long-wave UV dies not activate tagging

Drats....I interchanged my lamps and forgot about it.
Of course you need 254nm short wave uv for tagging.

The question why he can't detect tagging remains.. or is he looking at used stamps with tagging washed away during excessive soaking?