The amount of letters at the start of the exchange-name which stood for the exchange’s ID-number, varied from country to country, and even from city to city within a country! The number of letters was usually the first two or first three in any given exchange-name. In the United Kingdom, three letters followed by four numbers (3L-4N) was the rule. So ‘Whitehall 1212? would be “WHItehall 1212?, or 944-1212.In the United States, by comparison, phone-numbers followed the 2L-5N (two letters, five numbers) rule. This meant that the first two letters of the exchange-name stood for numbers. Notable exceptions to this rule were cities of New York, Philidelphia, Boston and Chicago, which followed the British example of 3L-4N. This brought up exchange-names like ‘PENnsylvania’, ‘TREmont’ and ‘ELDorado’. Since the rest of the country did 2L-5N, this could create some understandable confusion to people who weren’t from the US. East Coast. Eventually, these cities conformed with the rest of the nation, altering their phone-numbers so that instead of the above, they had numbers like: ‘PEnnsylvania 65000? or ‘ELdorado 51234, to avoid confusion.
Incidentally, PEnnsylvania 65000 is STILL the phone number of the Hotel Pennsylvania in New York, as it has been for over 90 years! Link -via TYWKIWDBI