Start w/ the VIN on the door jamb and SPID on the glove box door. Do they match? The VIN has a digit identifying the year. There's a VIN decode page on this site.
Post some pics and people will come out of the woodwork to explain what features ID it as what year or years. We love pics.
69 and 70 were very similar but I think each had a slightly different inner grille. 72 doors have a hole for a countersink bolt under the wing window. Early years had different wing window latch things.