Originally, WWIVnet nodes were numbered by area code. The format was txyzz, where x and y were the first and last digits of the area code, and zz was a number that started with 00 in area codes with a second digit of 0, and 50 in area codes with a second digit of one. t would start at 0 (although leading zeros are not quoted in node numbers) and would increase each time zz filled up. Thus, node 5802 was a node in area code 508, 6754 was a node in area code 617, and 12263 was a node in a very busy area code 212.
The renumbering of WWIVnet occurred sometime between Feb. 1993 and April 1993 -- the rule that area codes would only have second digits of 0 or 1 was changed and most WWIVnet nodes were renumbered into a zone based scheme. Node numbers were then of the format xzzz, where x was the zone number.