I think they were just making some more. I bought mine in early July, so I guess they were just out of them for a while.
Now it may just be my rifle, 'cause I'm one of those guys who often ends up with the odd gun that doesn't shoot the way it is supposed to (I have a thread on my Henry that shoots way to the right), but I found that Miroku tang sight works great at 100 yards or so, but there isn't enough elevation to hit anything at 250-300 yards. I've been toying with the idea of ordering a taller stem, but then I consider that 100 yards is probably all I really need with a '73. I have a '76 for the longer stuff, and Marbles charges an awful lot for just a stem.