I miss my former 3572.50 "hesalite sandwich" I sold a while back and it's annoying to wait & find a complete set in new-ish condition, so I made my own.
Got in a new 3861 hesalite and replaced the caseback with a genuine one from the sapphire version before removing the stickers or sizing. Very easy and doesn't require replacement of the movement spacer ring and addition of another gasket like on an 1861 conversion; it's a simple caseback swap for the 3861.