sam1234
358
1993
Prior to 1993, Patek offered the 3940 only with a solid caseback, and the 3941 with only the sapphire caseback.
Starting in 1993 the yellow, rose, and white gold 3940 were supplied standard with both a solid and sapphire back. The platinum version, to the best of my knowledge, was never factory equipped with a sapphire caseback.
Hope this helps.