There seems to be a lot of confusion on the ‘net about Aquadive Model 50 watches and who made them. It appears they were redialled Jenny watches.  There is also a version of this watch with Rotary on the dial.

This electronic watch has a highly modified ESA Dynotron movement. The watch has an additional depth gauge hand that’s attached to a circular copper pressure chamber (Bourdon tube) around the outside of the movement; the front of the movement has been modified to support this extra functionality. It’s not clear whether this was an ESA modification or whether it was carried out by the watch manufacturer.

Examples with working depth gauges are rare and these watches are now much sought after. They date from about 1970.

This first block of photographs shows an Aquadive Model 50 with a modified ESA 9154 movement.  You’ll notice that the dial lacks a window to display the date, so the normal ESA 9154 date mechanism is missing from this movement:

 

The second block of photographs is from another Aquadive Model 50 but this one contains a modified ESA 9150 movement. There are several indicators that this is a replacement movement: firstly, the date mechanism is still in place although there is no way to display the date and secondly, the battery clamp is from a Tissot.  I suspect the original 9154 died and was replaced with a working 9150 — these two movements are nearly identical although the 9150 has a lower beat of 21,600 bph compared to the 9154 running at 28,800 bph:

 

Some notes on dismantling this movement (refer to the photographs above):

1. Remove the small pressure gauge sensor “plug” between the top lugs.  This is a push fit into the main case. The “plug” has a flat on one side to help with its removal.  Never poke any sharp objects down this hollow “plug” otherwise you run the risk of puncturing the rubber seal in the Bourdon tube.
2. Remove the Bourdon tube by undoing the two large, recessed screws in the brass block of the Bourdon tube.  Do not undo the third screw that is flush with the top of the brass block as this is for filling the Bourdon tube with oil.  Carefully remove the Bourdon tube making sure it is free from the depth gauge actuating arm.
3. Remove the crown and stem as you would for a normal ESA 9150/4 movement.
4. Remove the large circular movement ring by undoing the two movement clamp screws.
5. Remove the movement and dial from the case. It should drop out easily.
6. Remove all four hands.
7. The dial is a press fit into the depth gauge plate; the dial feet locate with nylon bushes in the depth gauge plate — no screws
8. The movement is attached to the depth gauge plate in the same manner.  The movement has two posts in the dial feet holes (see photos above) and these posts locate with nylon bushes in the depth gauge plate — no screws
9. The rest of the movement is now dismantled and serviced in the same way as any normal ESA 9150/4 movement.