Bundy saxophones are the beginner line of the great Selmer saxophones. Henri and Alexandre Selmer began making reeds and mouthpieces and, after moving to New York, began building horns. After some success they were able to branch into multiple horns, as well as professional, intermediate and beginner lines.
Examine the metal of the saxophone. The darker the metal is, the more copper present, which is a signifier to an older horn. Copper is expensive and has been limited to trace amounts in modern horns as a cost-saving measure. Be sure the metal is not dark because of tarnish. If the horn is silver it is not only old but rare, as Selmer rarely used silver except on C melody horns.
Distinguish the key design. If there are keys on the left side of the bell, it would have been manufactured before 1940. If there is a high F# key on the top left stack, it was built most likely after 1970. There are several small key guard designs that can be identified by looking at graphics in the history section of the Selmer Company website.
Look on the back of the horn underneath the thumb rest or the left side of the bell just above or below the band. You should find a serial number. Bunny IIs are well documented and can be identified by year. Saxworx.com has a chart with serial numbers and years made.