If you look at the ASTM A407 spec, you will find this wire refered to as upholstery spring wire and lacing wire. It is a hard drawn spring wire with lower mechanical properties than ASTM A227 hard drawn. With spring wire, you will generally not find a chemical composition comparable to an SAE steel grade, with the notable exception of 9254 chrome silicon wire and the various grades of stainless wire. BTW, SAE used to publish spring wire specs, but they were shelved some years ago in favor of ASTM specs.