Apologies for the image quality. I got as close as possible to highlight the cuds, and focus and lighting both suffered in the process. Doubtless others can post better pics.
At any rate, this error seems as prevalent, at least in this batch of coins, as the big ww2 cud was. Nearly half the batch had them, all but two fully formed.
I don't think I've seen a cud in this position before. Some of these coins also have the usual suspects in obverse cuds, but none seem to have other reverse errors on them.
(http://goo.gl/iUKcd)
I think I have a couple 50c with a small cud on the Roo's upper arm, but haven't done any images of them yet, so not sure of the year.