Until 1939 the same piece was pitched differently in every city.
Concert pitch was negotiable for centuries. Handel's tuning fork sat around 422.5 Hz, Beethoven's near 455 Hz, and France fixed 435 Hz by decree in 1859. Only an international conference in 1939 recommended 440 Hz for the A above middle C; in 1955 the ISO turned that into a standard, today ISO 16.
Useful: If old music sounds odd to you, the tuning may be the reason, not your ear.
Source: en.wikipedia.org