Maybe I'm just looking past them, but that would be hard for me to imagine.
I'm a very serious gun guy and hobbyist. I hit numerous gun stores and gun shows and I just hardly ever go if I don't have time to look over ALL the handguns offered for sale. (of course, only the used ones. I almost never look at cases full of new guns)
My point is that I just don't hardly EVER see Security, Speed and Service Sixes in my travels. Really, no BS. I see GP's out the yingyang. I hardly ever see any of the 'Sixes.
First center fire revolver I'd ever shot was a four inch Security Six stoked with .357 Magnum. I was addicted at the first BOOM.
I'd pick one up if I find one with a price that makes me smile. Just to have yet another .357 Magnum. I absolutely love 'em, and love the cartridge.
Attention Brass rats and other reloaders: I really need .327 Federal Magnum brass, no lot size too small. Tell me what caliber you need and I'll see what I have to swap. PM me and we'll discuss.