The Secometer was based on the same 6/0 sized, 17 jewel 987S movement that military watches used as well as the 1940 Sentinel. In fact, the Secometer and the Sentinel share the same case. I believe the Sentinel was offered in 1941 with an AGN dial - but without a second hand. However, I've never seen one and I'm not sure I could tell it apart from a Secometer unless the dial pattern is different.
Anyway, the Secometer came in a 10K gold filled case with an AGN dial as shown above. The case is prone to wear through on the tops of the lugs and case back lip.
Since the Secometer has the 987S, the movement will hack, or stop, when you pull the crown out to set the time.
I recently overhauled a 1946 Secometer project watch so let me show you how it went...
First, as received the watch was missing it's minute hand, second hand and crystal. I put a new crystal on to protect the dial while the watch waited it's turn for some TLC.
The dial is an old, but well done, refinish. Just needs a little cleaning to look great again.
Dials are held on by small screws in the side of the movement that bear against the dial feet attached to the dial itself. A 987S has three dial feet locations.
With the dial removed the hour wheel and cannon pinion can be removed. These are the parts the hands attach to. You can also see the seconds hand pivot sticking out of the center of the center wheel shaft.
What makes a 987S different than a 987A is the addition of the seconds wheel and pinion on the back of the movement. This allows for a sweep second hand instead of a sub-second hand.
The two screws that hold the spring arm that secures the second hand pinion and shaft are tiny. Getting them lined up to go back in takes a gentle touch or they can spring off into space, never to be seen again.
Here the second hand pinion and shaft is standing a little proud of the back. It just slips right out.
With the seconds wheel removed you can see the pivot that it attaches to. At this point the movement is pretty much the same as a 987A - except that it has the parts to "hack" still inside.
With all the mainspring tension let off, the mainspring winding wheel is removed.
The bridge is removed and you can see the mainspring barrel, center wheel and third wheel with the extended pivot for the seconds wheel
The next bridge is removed to reveal the fourth wheel (the seconds hand on a 987A would attach to the fourth wheel) and the escape wheel. All the wheels can all be removed now.
Here's good shot of the linkage that will hack the watch when the crown is pulled out to set the time. The little bent section near the balance wheel is pulled over and it hits the balance wheel to stop it. Push the crown back in and it moves away from the wheel - as shown below.
With the balance and the pivot fork assembly removed the back of the watch is cleared off.
On the front side, the keyless works and cap jewel are removed. Everything is separated for a thorough cleaning.
While stuff cleans, a fresh mainspring is installed and lubricated.
I'm always surprised at how dirty the cleaning solution gets after the parts are ultrasonically cleaned a while. I use several series of cleaning solutions to get the parts throughly cleaned.
Everything is laid out to dry and be lubricated during assembly.
First the pallet fork goes back in. Every jewel gets a tiny droplet of oil.
Here the pallet fork bridge is installed. Getting everything properly lined up is the key to putting a watch back together. If it doesn't fit smoothly and perfectly then something isn't lined up right. Force will not fix it - it just breaks the part that's not lined up right. The two pallet jewels also get a droplet of oil.
Now the escape wheel and fourth wheel go back in.
And their bridge is reinstalled - again, everything has to line up right.
Now the third wheel, center wheel and mainspring barrel go back on.
And their bridge is reinstalled.
The seconds pinion and shaft goes back in and the mainspring winding wheel is reinstalled. At this point a few turns of the crown will put power back into the gear train.
I prefer to put the balance on before the seconds wheel - that way I know the watch runs before I try to put the wheel back on. If I have problems after the wheel is installed I'll know it's the wheel and not elsewhere.
With the seconds wheel reinstalled, the assembly goes onto the watch timer ... 30 seconds fast per day. Not too bad but a slight tweak to the regulator can slow it down.
The cannon pinion and hour wheel are reinstalled and the keyless works greased.
With the dial back on and replacement hands - the watch goes back together inside the freshly polished case.
And now the prerequisite wrist shot of the completed project. Ready for another 60 years of service.