Orient Vintage Diver 1984

Mysterious Bezel Markings explained
I took me quite a while to figure out the meaning of the numbers on the inner turning bezel 20M, 30 M, 35 M and 40 M in different colors. I knew it had to do something with non-decompression times as always on divers. Finally I found the solution with the help of some dive tables on the web: The meaning of the markings are as follows:

   20 M    You can stay at 20 M depth during 45 to 60 minutes without decompression
   30 M    You can stay at 30 M depth during 30 to 45 minutes
   35 M    You can stay at 35 M depth during 15 to 30 minutes
   40 M    You can stay at 40 M depth during 0 to 15 minutes.

Example: Below is a picture assuming that you dove directly to the depth of 30 M and have set the    30 M    marker at 17:23 at the start of your dive. Now it is 17:25 and you can read the remaining time you can dive at 30 M without need for decompression, in the example shown, about 28 minutes left to 17:53 (00 Marker).