Don, I, too, have a 1 cent postage due that puzzles me. It is just as you described, and I share your feeling, that it's not my kind of luck it'd be a J29. (I've quite a bit of Irish in my family tree.)

The perf is 12, the color is tricksy, and there is no watermark. I used a light, as opposed to Clarity, seeing as how, at the bottom of the stamp, it appears the ink is already somewhat smeared, though from printing or age I do not know.
I really didn't look too hard at the stamp itself, being that I am organizing according to cancel, but even that is proving difficult for me. About all I can say is, it's a cork cancel.

Then, I've this 2 cent, same thing, but with a manual cancel.

Hey, at least I do have a couple of postage dues represented in the collection, to go in the back of book section. It's kind sparse, at the moment.