I have this 1971 D Roosevelt dime and I think this may be a transitional reverse. The flame on top of the torch has more detail then others from that year. I know of none found past 1970 but this may be one. The first three pictures of the flame are from my 1971 D. The last four pictures were borrowed from errorref.com showing the transitional reverse.
I think your on to something Mr. Coop. The dime I have shows the line in which you illustrated. One other thing I notice on the reused proof reverse is the proximity of the top of the flame to the bottom of the S in STATES. Same as the 1971 D.