This one is marked 14K GOLD FILLED as opposed to the one noted in Desmond's article, which was 10K GOLD FILLED. Desmond's review on these ultra rare Seamasters can be downloaded with the link below. http://www.mediafire.com/file/jimntjnnjkz/Rare Seamaster Prototype 560.pdf
Haven't seen many of them! Maybe 2 others over the last 5 years and the last was on WUS a couple years ago. It's pretty cool how they used a crystal for a display for those salesman's samples.
I would love to convert my 561 Connie to a see through back (while keeping the original back in a safe place). These 5XX movements are exceptionally beautiful.
Yes, the majority of these SMDV's were in front loading cases. It supposedly helped with water resistance, and I was told that when made in 14 or 18ct Omega could use less gold in the case because of the design. Kyle had/has a Seamaster display back from a screw on case back bumper model. That was a logical choice because there was no observatory medallion or hippocampus logo - just a plain flat outside.