It's quite a well known historical style for pilots' watches from the very earliest days of flying (notably by Zenith), but one of the most famous examples of it is this IWC style from the 1930s which I think is what Patek were imitating:
Funny you should mention Zenith pilot watches.
Only this morning I purchased both of these via the LVMH employee sale (my daughter works for Belmond in UK) not the watch I was hoping for but always liked .
Yeah, I know it's all El Primero this and that these days but IIRC Zenith still hold the patent for a "Pilot" watch and are apparently still the only brand allowed to put "Pilot" on the dial.
It's quite a well known historical style for pilots' watches from the very earliest days of flying (notably by Zenith), but one of the most famous examples of it is this IWC style from the 1930s which I think is what Patek were imitating: