One saw blade will do a LOT of frizzen facings. When I find one at a flea market or wherever that is just worn down to nubs, I think it's an ok sacrifice for frizzens, small springs etc. considering how many other functional hand saws I have of the same age.
These should all be straight high carbon steel, no weird alloys as I'm pretty sure all of mine are at least 80-100 years old. Couldn't tell you the alloy but they're some tough stuff and boy do they spark.
I would be leery of newer saw blades for this purpose largely because a lot of new saw blades - sawsalls, bandsaws etc are made of multiple steels that are electrowelded (or whatever the proper terminology is) of multiple steels and you're going to get different steels in different portions of each blade.