A440 is our standard. Nerveless, standard pitch variations remain around the globe. Here is a short expose on past and current pitch variations.
There is a Chickering piano I tune regularly that has embossed on the plate, "International Standard Pitch A435" That is 20 cents lower than A440; A pitch established in Paris in 1880. Montreal Symphony officially uses A442 , 8 cents sharper than 440. At the turn of the century the Steinway factory would deliver pianos at your choice of "soft pitch" or "hard pitch" , being a440 and A452(48cents sharper) respectively. A452 was the official British Military band pitch. I own a C melody saxophone from 1917 with tuning fork symbol and the words "low pitch" stamped on the back. "Low pitch" is A440. Thus far I have discussed a 70 cent range, nearly a full semitone.
It is worth taking note of current variations. I have seen musicians get into trouble. I recall a show I was tuning for at Maison de Culture in Gatineau. A first show of a tour. They were using some tracks with recorded string players and some orchestral instruments. Apparently they had the trax produced somewhere In Europe, and they were at A444. They did not realize the significance of this until their first sound check with a piano at A440, 16 cents lower.
This reality has implications for our understanding of "perfect pitch". With historical variations of over a semitone, it appears not to be absolute, but simply an extraordinary memory for whatever one has been exposed to over time.
In conclusion, here is a brief overview of some historically significant pitch references.
Take note that at A400 , one HZ variation to A441 is 4 cents. There are 100 cents in a semitone. This is an approximation for Hz graphed against cents it in fact an exponential curve.
Never less if you consider that a full semitone is approximately A 415 to 440 you will appreciate the variations below fully.
c. 1715 A= 419.9, England. Crude tenor fork, possibly made by John Shore, the inventor of the tuning fork.
1751 A=422.5, London. Handel's tuning fork. The box which contains the fork bears the inscription: "This pitchfork was the property of the Immortal Handel and left by him at the Foundling Hospital, when the Messiah was performed in 1751."
1780 A= 421.3, Vienna. Tuning fork of the Saxon organ builder Schulz who lived in Vienna during Mozart's lifetime.
c.1820 A=433, London. "Pitch approved by Sir George Smart, conductor of the Philharmonic
1829 A=425.5, Paris. Pitch of the piano at the opera
1839 A=448, Hamburg. Opera pitch.
1859 A=456.1, Vienna. Sharp Vienna pitch from a fork in the possession of the Streicher Piano Co. The Viennese orchestral pitch as used before the introduction of the French Diapason Normal.
1878 A= 436, London. Standard pitch of church organs taken from Metzler's tuning fork
1880 A=444.9, London. Her majesty's opera. From a tuning fork of the theatre as measured by Hipkins
1880 A=446.2, London. Tuning fork used by John Broadwood and Co for in house tunings but not for public concerts.