I’ve been meaning to share this for a while (I can't remember if I have done so or not, now I think about it).

Anyway, please see my period Heuer tool No 033, for use in opening a Monaco.

Unknown to most Heuer collectors the elusive tool 033's can be obtained from most toy stores, although some Heuer collectors may be able to raid children's (or their own) Lego (I say l-a-y-g-o, some say l-e-g-g-o) collection.

The first rule of any advice, however, is to completely IGNORE the advice. These are specialised vintage watches and only service specialists should be allowed near them. OK, now my disclaimer is out of the way, if you're a thrill seeker, here are the tool 033 usage steps:

1. assemble your tool 033. Any colour bricks will do , but I've had my best results with the pictured red and grey pieces.

2. see pic- be sure to align your Monaco with the lugs over the bricks. Some slight splaying of one brick tower is necessary to fit your Monaco in between the two brick towers.

3. (un-illustrated) carefully push down evenly with your thumbs on the corners (strongest points) of the glass and push downwards. The caseback/movement/dial/glass section will click downwards and the upper outer case should be left on your Tool 033. You may need a couple of gentle pushes to achieve this. Usually one side (ie the 12 o'clock side or the 6 o'clock side) will click out first.

WARNING! Be careful not to damage you Monaco's dial or hands when pushing down and the two pieces of case are separated. Gently and steadily is best!

CAUTION!: old Monaco seals bleed, so be careful that if opening your watch you're sure the seal has not bled- you might lift the dial paint away from the dial.

4. for re-assembly, carefully replace the seal and glass (note, vintage Monaco glass's are slightly un-square, so will fit properly only if replaced in the same orientation as taken off) on the movement and dial section, place this ON A FLAT SURFACE, and then place the outer case (and bracelet as in the pictured example) over this section and push the outer section down carefully.

5. check the seal has not pinched when both case pieces have been mated together.

BEWARE! Vintage Monaco’s are by NO MEANS waterproof- do not swim, shower, wash hands with one. Water is the enemy of the vintage Monaco- they are susceptible too to sweat- so make sure your seal is intact and has been reassembled correctly.
Here are a couple of quick pics of the Mk II/Transitional Monaco (what are we calling these?) once Tool 033'd. I should try to get some clearer ones.

Have fun!
Cheers

Stew.