2 Scans showing both sets of lugs looking in and serial / ref fonts , then also flat side view of crown guard ?
Fwiw I always ask for a ruler to be placed horizontal to the lugs so you can measure roughly the thickness of each lug ?
Looking to see that all four lugs are even and assess any loss of metal structure , same with crown guards make sue both are even and again look for structure loss , the crown is easy , if you want to return to the twin lock u just buy a tube and crown the only thing to remember when fitting the tube on a twin is that u should use the correct tool to remove the fitment tabs (or do by hand I'm sure there is a technical term for that but buggered if I know)
Tube and Crown as EASY , replacing metal structure loss is not , and viewing the dial from different angles is criticle as the real beauty of that watch is the dial , there is most of the value so really get better scans , so easy to hide dried moisture dots , scratches blemishes etc ...
Just my humble thoughts fwiw , mileage will vary
Anyways good luck on your hunt , the Bart's are über KOOL