After a trip to the local jewellers, casebacks safely swapped. With a movement this lovely, it's criminal to hide the beating heart of this watch, although it did feel weird removing the 'Flight qualified' wording....
So, after too long, my most ambitious bit of tinkering yet. My first three register chronograph service - Lemania 1387 (Omega 681). My first replacement of a mineral crystal and I had to replace the hour recorder hand. The nearest Omega one was too light in colour so I had to mix 3 parts Humbrol 48 to 5 parts Humbrol 47 - that experiment took a few dummy runs. Also had to broach the Omega hand to get it to fit (another first)