If it's older than 70+ years, which it appears to be by the looks of the bulky construction and parabolic heads, and you mean other than the name of the mfgr (which you've already identified) and logo (/B\), it's probably various nut and bolt size systems (e.g., "U.S.S.", or "S.A.E.", or even the word "nut" or a hex symbol).The wrench has some interesting markings on it.