Created in 1977, Caliber 240 is arguably one of the most iconic horological movements ever produced. Along with its variations, it is currently housed in as many as 25 Patek references.
It's been the soul of most Rare Handcraft models we have seen in modern times, which include (among others) the out-of-catalog references 5075, 5077, 5086, 5089, 5177, 5189, and 5738, as well as the in-catalog 5088, 5131 and 5231 (the last two with the obvious "HU" addition for the Worldtimer complication), and again 5738!
Cheers, FabR