I ended up forging that anchor into a machete-of-doom (1/2" stock is a little unnecessary for any blade unless you intend to draw it out into a longsword). Unhardened it could cut deeper into scrap pine than a hatchet that was lying around the shop (crosscut, not rip) and the steel proved to be water hardening, so I'm going to try and oven-temper it and see how it works after that.
I've been impressed so far, but good luck if you don't have a striker or a power hammer. It will probably all make perfectly nice blades (except rr spikes, not a fan of those personally) it's probably up to what is available and closest to your end product. Springs are great for their consistent width and (if a leaf spring) straight shape, I've personally never had the patience to straighten out a coil spring with other material available.
Sorry, kind of rambled off there. I think the best answer is if it hardens with water or oil, give it a shot and see how it goes. Masonry tools work well as stock also.