Hand-fettled aeroplanes
I did wonder about that.
I often muse on the scene from one the 'Dollars' films - the Spaghetti Westerns - where the man with no name goes into a gunsmiths and fiddles with (Colt?) revolver components, fitting them and spinning them, until he finds a set where the manufacturing tolerances have lined up in favourable coincidence. IIRC he then holds up the shopkeeper with it in lieu of payment....
I suppose this might be seen as a reversed parody of some defence acquisitions?
As I used to say in lecturing days: Discuss.