I found a Single Six- actually a Super Single Six for sale. It has an interesting serial number. D553553. Now from my novice research, this should not be a "D" serial number. I called Linda at Ruger, she showed no "D" on their transcribed computer database for a Super Single Six. Add to that the "D" seems to be very crudely stamped. The gun is in fair/good condition, but there is no box or paperwork- so as a collector's item there is no real value… but it has caught my interest. Any ideas?