Plot Summary?

Shortly after the Second World War, Max, a transplanted American, visits an English pawn shop to sell his trumpet. The shopkeeper recognizes the tune Max plays as one on a wax master of an unreleased recording, discovered and restored from shards found in a piano salvaged from a cruise ship turned hospital ship, now slated for demolition.

If he was born in 1900 and was 24 when he and Max met, how can it be shortly after WWII? Just something I found that was funny.