Air Canada has fin numbers for their aircraft. Each type of aircraft has a range.
747 combi's are 341,42,43 ex-CP 381,82,84,85
320's- 201-232 ex-CP 401-416
319's- 251-28? 737's 500 series
DC-9's- 700 series F-28's- 100 BAE-146's-200 series
767's-600 series Dash8's 800/300 series.
One of these numbers will appear on the tail and front gear doors of AC aircraft with the registration on the fuselage.