This is perhaps the only one of these watches I have seen with the sapphire crystal and a black matte dial showing the 4000 ft depth rating. I have seen Submariners with this combination but never Seadwellers.
Also note the dial does not have the luminous markers that are surrounded by the white gold rings.
The serial number 7,471,xxx dates the watch to 1982!
The watch is the first Sapphire crystal Seadweller made, the reference 16660, and is the replacement for the first model Seadweller, reference 1665. The watch differs from the Submariner in that it is waterproof to 4000 ft and features a helium escape valve to allow finer sized Helium molecules to exit the watch case as diver ascend to the surface after saturation dives.
The watch is in overall excellent condition with typical light marks from being lightly worn. The bracelet fitted is the correct Seadweller bracelet reference 93160 with the solid end pieces and heavier hardware.
The movement was not serviced by me as it keeps excellent time.
The watch measures 40mm wide (excluding the crown or crown guards) by 48mm long.