On our dept the numbering system is pretty basic. We have 3 pumpers numbered 1, 2, and 3. One being the newest and 3 being the oldest. Our tankers are 1 and 2 our rescue truck doesn't have a number and our quick response (grass rig) is QR. Our ambulances our numbered in order of how we have bought them. Every member has a number depending on seniority and another set of numbers according to rank i.e. cheif is 600 and then down the line from there.
As you can tell we our a small volunteer dept. 30 members in a town of 3500.