Since the 29-4 only lasted 2 years appearing in 1988 and disappearing in 1990 with the introduction of the 29-5 I wouldn't call it odd as much as I'd call it scarce.
I have two 3" model 29-4's, they both have the full underlug and un-fluted cylinder. I think they made quite a few of them, but I haven't seen one in 8 3/8". Not really a odd duck. They are very heavy when loaded.
Chop
29-4 8-3/8 "classic hunter" product code #101254
2500 manufactured in 98
the 29-4 3 inch..2532 made in 98 also..
So they are not "odd" but the term " scarce" would work well...