Need info on the steel of my Spyderco}}

I don't have any experience with the 420's, but I do have an ATS55 delica. ATS55 seems pretty tough, I have never chipped it or damaged it.Its edge retention is pretty good. I hone mine about once a week but it doesn't need it very bad. You can get it shaving sharp easily with a little practice. Don't use a honing strop on it very much at all because it is very easy to roll the edge. A fine white ceramic or surgical black arkansas stone will work much better.Corrosian resistance is also very good. I don't use mine in any extreme enviroments but there isn't a bit of rust on it and I've carried it in my pocket every day for a year now.Hope that helps.

Fix it right the first time, use Baling Wire !
ATS-55 is a high carbon stainless, most of the 420 stainlesses are medium to low in carbon. Basic 420 (sometimes called 420 J2) is down around .35% carbon while 420HC (Buck knives and Swiss Army knives) is around .50% carbon. ATS-55 is around 1% carbon. This is comparable to 440C, but they have a some minor alloy differences. I think the differences should make ATS-55 a bit easier to sharpen than 440C.
The little booklet that came with your knife should have about 5 pages worth of metallurgy info. in it.
ATS-55 was made by Hitachi, supposedly specifically designed for the knife industry. This steel is comparable to ATS-34. Not QUITE enough experience with either to compare the performance of the 2. 420, for a working knife, is crap. If you look around the forums here, you'll notice that almost NO knives mentioned are 420. Those that are are quite obviously collectors' knives, such as Gil Hibben's work. I don't own any knives using 420 for this reason. If you want a low-care wall-hanger, it's great. Just don't expect to be able to use it to cut your way out of a paper bag. Spyderco, to my knowledge, is the only company using ATS-55. I apologize if that is incorrect.