Simonds Diamond-S Knife Steel
Composition Analysis Graph, Equivalents And Overview

Diamond-S(Simonds) - Water hardening tool steel. Quite popular with custom knife makers, beginners and seasoned experts alike. Easy to work with, decent edge holding and ok. toughness, depending on the heat treatment. Maximum working hardness is in 63-65 HRC Range. Obviously, you won't be getting much of the toughness at 65hrc, however edge holding and cutting performance for thin edges increase accordingly.
W1 is used pretty much for all sorts of knives: folders, kitchen knives, bushcraft, etc. The main issue with AISI W1 standard spec is that it is very broad. To be specific, allows carbon content from 0.70% to 1.50%. For carbon that is a huge range. Steel properties will vary very significantly from 0.70% to 1.50%. If you are thinking of a custom, or considering buying one better find out exactly what batch and what composition. 0.70% Carbon steel won't get as hard or strong as 1.20% or 1.50% steel, or even 1% Carbon steel. On the other hand, if you want large, tough knife, may be 0.70% will do too. If you trust the maker, you can leave the choice up to him. Personally, I'd really want to know exact composition of the steel used in my knives.

Manufacturing Technology - Ingot

Country - United States(US)

NOTE - Approximate composition based on manufacturer's or standard reference information and other alloys in the same reference group is shown.

^* - Listed as an equivalent or replacement for alloys in this group.