I am checking my samples of 2187.
2187 40¢ Claire Chennault overall tagging, dull gum
2187a 40¢ Claire Chennault PP coated, solid tagging, dull gum
2187av 40¢ Claire Chennault PP Coated,. Grainy solid tagging, low gloss gum
2187c 40¢ Claire Chennault PP Uncoated, mottled tagging,shiny gum
This is from Esrati's listing (20th revision)
I have 3 with shiny gum although I purchased one claiming to be low gloss gum.
Using Esrati's comment about 2187b (assume now called 2187c), I could identify it with both the striated gum and blue white under UV.
I have two others without striated gum and this show greenish-yellow so I am wondering if I have the unlisted Scott variety since Scott does not usually catalogue based upon color under UV or striated gum.