That Platinum IWC Mark XII

The Horologium September 16, 2002 admin



The Mark XII is one of my favorite watches–utterly straight forward and perfectly proportioned.

I did a Horologium series on it, which included swapping out the original caliber 884 for a more nicely finished caliber 887.

I then came across a used Mark XII platinum case. Unfortunately, the threads of the screw back and case band were badly damaged, and the back was unusable.

My first attempt was to modify the original case back to allow it to be attached with screws. The original design, however, made it very difficult to maintain adequate water resistance because of the location of the original back gasket.

The answer has turned out to be an entirely new back. I purchased a 2 1/4 inch square of six gauge platinum 950 for US$1,800. (The trimmings returned about $700 of that and the vacuumed dust and chips from the lathe about another $400. The metals processor throws the vacuum bag into hydrochloric acid to retrieve the platinum. The steel and all other waste is dissolved.)




The watch, as shown here, is not finished. Final brushing and finishing is yet to come. The sapphire rear glass is installed, but barely visible in the photograph. The back is held in place with four white 18K screws. A groove cut in a vertical lip on the inside of the back seals to a vertical surface inside the case. The back is centered and positioned by the seal. Sealing is thus not dependent on gasket compression by the screws.

Platinum is a bear to cut and machine. The case has spent endless hours in hydrochloric acid to remove broken taps. I am not going to make another one any time soon.