I suspect its some sort of mfr special, I got some from sgammo at about the same price. FWIW, this ammo does seem to have a pretty heavy flash in my 4" model 64.
I suspect you'll be quite happy -
I just picked up my Robertson's 64-5 today
Mine was one of the $279 specials with "extensive scouring"... their grading seems very conservative.
The pic below is hi-res - you can click a couple of times to zoom way in & see more than you can in person. Not...