I'm not quite sure  what machine you are discussing as you refer to a set of disk.  Are you referring to a typical 1940-50 era disk? ( sometimes disks were referred to as disk harrows)
The Oliver disks of that era were identified as PA-(width in feet). The PA referred to Power Angle.  These disks  differed from most disigns in that you pulled forward to angel the disk and backed up to straighten the disk. If this is the model that you have, the frame was painted red in the 1940s.