I took a look at a white dial SS MUT at a local vintage watch store a couple of months ago (cal. 849 with white dial, arabic numerals and dauphine hands - same as the latest range I know), but to my surprise it had a SOLID back instead of the saphire crystal I was expecting...
According to the current JLC catalogue all MUTs have a display back, but now I'm confused...
Thanks for your help,
Kisgabi