I 've been looking at some old R-10 images, including some of my own images, and I'm finally asking one question: Why did some of the fans have 3 square blades while others have 4 pointy, tapered blades? It certainly looks funny.
I think it went something like this
shop worker #1 "Hey, this fan's broke"
Shop worker #2 "Go get a new one from the box"
#1 "Ok"
climbs down, rumages through box
#1 "hey, they're diffrent"
#2 "just put them on, nobody gives a dam so long as it works"