With regard to Johns response, I think some clarification might be in order. You won't get typical steel certifications from NJSB, simple because that outfit has all of its steel custom made at a plant in Germany. The way Aldo explained it to me is.... he orders to his specs/recipes, he gets a finished sample, and has it tested TWICE, (each time by a different lab) to ensure the makeup is as ordered. If it is, everything is fine, if it's not, he rejects the batch/run. If you pay close attention to NJSB website, there are slight changes to the "specs" of each steel as new batches come in (the makeup listed on the page of each steel). Most of the time the changes are tiny.... most times it's .00XX or less. And those numbers are derived from the tests they perform. What that means it that the listed makeup on their website is essentially a "spec sheet" for that given run/batch of the specific steel.
When it comes to actual "certifications" which are basically a guarantee of content/quality, there are very few that can/will provide that....and if they do, expect to pay a premium for it.
What most don't realize is that right now, "GOOD" steel (meaning tight tolerance/is what's it's advertised to be) is more difficult to obtain than any other time in my 30+ year career.
I agree with Niagra, Crucible, and would add Specialty Metals LLC (that's the folks who used to own/operate Crubilbe before it went under) and Kelly Cupples.
Personally, I've had far too many bad experiences with Admiral to recommend them.... I'll leave that one at that.
There are only three places I will purchase steel...... NJSB, Specialty Metals, and Kelly Cupples. Those are the sellers that I have come to trust, and after being burned, any other sources would have to prove themselves to me before I'd trust them. Each maker will have their own list of trusted sources....based on their own experiences. If you're new, it's just part of the game..... finding those sources that YOU trust.
My advice about buying steel is..... When you find a trustworthy source for what you want....buy as much of it as you can possibly afford. It's not going to get any cheaper, you may not be able to find/buy it later, shipping will be offset when buying in quantity, and it's not going to go bad on the shelf.