I'm sorry to say it but it's not going to be easy.
By: VMM : February 4th, 2018-04:31
The 1815 is 39,5 mm, smaller than that for a modern high end chrono is quite unlikely to find. Maybe you should try to find a nice vintage chrono, they used to be smaller back in the days. Right now the one that comes to my mind, a favorite of mine, it's ...