Tagging

I noticed that the PNC Club (http://www.pnc3.org/Default-old.htm) lists #2280 25¢ as block tagged with plate numbers of 1,2, 3,4,5,7,8,9. And that it lists #2280a as unevenly tagged with plate numbers of 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15.

Is it safe to assume that if I have stamps with plate numbers of 10 and up that they are 2280a?

I don't have a UV light (cheapest I've seen is around $50) ... is there another way to detect tagging (since I have several with PN 1-9 and won't know which they are)?

Thanks in advance

Durland shows both stamps printed with plates 1 through 9 but only lists Plates 10 through 15 under Scott 2280a. Rather than calling it "unevenly tagged", Durland lists 2280a as being "mottled prephosphored."

EDIT: The 2010 Durland addendum changes "mottled" to "embedded."

Cliffhiker, to answer your first question. Yes, plate numbers 10 and up have to be 2280a. All the "a" numbers are overall tagged.
Also the ONLY sure way to tell tagging is with a UV lamp. However, especially block tagging can very often be seen with the naked eye.
One of the easiest to spot ( in my opinion ) is the 25 cent Breadwagon coil in the Transportation series. On these one can almost always see the outlines of the "block". Other stamps are more difficult, but sometimes looking at them under an angle with backlighting can help.

Peter

Actually, overall tagged is a different thing - overall is applied after the ink is printed (on top of the ink). The 2280a are prephosphored - the tagging is applied at the paper supplier before the stamps are printed (under the ink).