The U is a new one to me, so something to keep an eye out for in the future.
The date ranges I have for the 45 devices are 18 May 1900 to 6 July 1903 for the large type, and 9 December 1903 to 3 December 1906 for the small type, so your examples extend those ranges considerably.
When you view what other collectors have managed to acquire over time, it hides the true rarity of things.
I have just looked through around 1,000 low value NSW stamps with no SPECIAL cancels that I could identify (I don't waste time trying to work it out, look at a cancel long enough and it will turn into whatever you want it to be).
Interesting timing, given Brown & Campbell's 2nd edition on NSW Numerals was also released in 1977. There is mention of an article by Frankenstein but it must've been tipped in as it's not in the book proper.
Thanks for sharing your collection Bobby De La Rue. Your second row shows that, notwithstanding point 6 in the Richard Peck article, canceller 44 was used with both the large and small 'Q Special' plugs.