Such a big moon phase window is quite rare (I don’t know if it was the case when it has been made) even today. I only have in mind the Arnold & Son HM Perpetual Moon and the Konstantin Chaykin Joker which can measure up.
Thank you for this discovery (at least for me).
Best wishes
Alkiro
6 Konstantin Chaykin listings are live on the eBay market and 0 collector listings on the WatchProSite marketplace.