In reply to Charles S King.

Several decades ago, most Rolex watches outside of its dive watch collections featured 50m depth ratings, but that has since been updated to 100m across all models (excluding the Cellini series). The first Rolex Oyster Perpetual Air-King reference (the ref. 5500) had a 50m depth rating when it appeared in 1958, and by the time the second generation arrived in 1989, the Air-King had been updated to have a 100m depth rating. There is a chance that the Air-King 5500 might have been marketed with an updated depth rating near the end of its production simply due to how long it remained a part of Rolex's catalog, but the actual design and structure of the watch did not change at all.