If this was photographed through mint packaging, I'm thinking reflection. There is a known RPM for this date and mint mark, though, so I'm hoping I'm wrong.
I found it very difficult to get a better photo because of the reflection. This half was taken out of the proof set. I think your right about one other known RPM, but it is an S/S South, and a RDV-003 (straight G). This is an RDV-002 (flared G). Larry Nienaber
:smileLarry I think you have found 1 more 1968-S Kennedy Half RPM!?!?! Not an Expert but+Not Blind:kewl:
repunched with a glob of metal. Looks like a filled die error to me. Although Im no rpm expert either. They will come though...patience
Just to follow up on this post...I sent this 50c 68S to James Wiles and got it back as a new listing, 68S RPM-002, S/S North. Larry Nienaber