Looking at this Sandcast, it looks very correct for the Vin range. The only thing that seems particularly too good to me is the condition of the seat. I own two unmolested bikes with both having less than 17k miles and the seats are collapsing in the driver area from wear as the red foam just didn't hold up well. The seat conditions on my bikes show a depressed area, and with 52k on this one, I would expect more deformation. Not to say the riders of this Sandcast might have been light weight individuals or maybe the seat had the foam replaced at some point in time, don't know, just my input.
Curious, the owner states in the video that to the best of his knowledge, this is the only other sequential frame engine combination know, but Vin 928/E929 is listed in our directory.
Our directory also has 1356/E1374 paired together, and this auction is showing 1375/E1374 paired. Maybe the directory is wrong, don't know.
My thoughts,
DW