Hi Battleship, I have a ton of these but I'm away for another 10 days. Is this a perpetual search? How many do you want? Do you have a limit. (If my memory serves correctly, I believe I may have 200 - 300 or more of these...)
@ClassicPhilatelist - All of 'em good sir! Most definitely perpetual as this will indeed be an extensive long-term study requiring the collection of a many RB23. I await patiently for your return from "away" good man ;-) Chat soon, cheers.