Three 1/4" low shank sewing machine presser feet

These are the three presser feet that I have found in my attachments that make a perfect 1/4" seam for quilting. I think they came in some of those metal and plastic attachment tins that we've picked up at yard sales over the years...possibly from 60's or 70's era sewing machines? I use them all the time on my Singer 15-88 treadle, Featherweights, Singer 27 treadle, electric 1940's/50's era New Williams machine, etc. One of them has little markings on the end of the right side. I have no idea what those are for...any ideas?