First, they way they do orders...
They'll announce on their forum that there's a new knife coming up for sale, usually "soon." There's a running joke about "two weeks" and Busse Standard Time (BST). Then, after however much time passes, they'll announce that it's now up for orders. They'll take orders for somewhere around 4-6 weeks, again Busse Standard Time, so who knows, and they post a last-call after which time they stop taking orders. Then they start making knives and filling orders. Then, after some more Busse Standard Time goes by, they'll repeat the process.
Now, for the steels...
Most Scrapyard knives are SR-77, which is a properly heat-treated version of S-7, a shock steel used to make jackhammer bits.
The current knife, the Scrapper 5, is going to be SR-101 steel, which is Swamp Rat's regular steel. I think it's a modified ball-bearing steel, possibly. The same thread I got those pics from, also had pics of the same guy doing the same things with a Swamp Rat knife, made of differentially-hardened SR-101, with equally impressive results. It just didn't bend over as much. The Swamp Rat M6 pictured in my previous post is differentially hardened SR-101. That knife feels like an absolute tank. I bet I could stab my way through a brick wall with it if I had to.
The Buck Nighthawk is made of 420HC, which is a version of 420 stainless, a mediocre blade steel. However, with Buck's heat treat, it ends up being a decent steel, and this knife is capable of taking a lot of abuse. I hereby proclaim that, for the money, the Nighthawk is a good knife.
All of the Kabars I've ever used were made of 1095. I believe there are a few now made of D-2 as well.
And you can still go buy their knives at inflated prices on Bladeforums and ebay anytime you want! They also have a guy who makes the gunshow circuit somewhat and sells them. I've bought a couple at the local Indy 1500 Gun & Knife show. They typically have a large table/booth setup at both Knob Creek and the Bladeshows. There's also the Busse Company Store, operated by some guy out west, that sells them as well at company pricing. But you're always limited to what they have on hand. You won't always find these:
edited: A Ground Pounder. Sweet. I like Grayman Knives. If I wasn't so addicted to Busses I would probably order one.