The front name plate around the front lens element will contain the lens model "CANON ZOOM LENS EF 24-70mm 1:2.8 L II USM". Check to make sure it is the mark II version.
Technical Specifications
General:
- Focal Length: 24-70 mm
- Maximum Aperture: f/2.8
- Minimum Aperture: f/22
- Closest Focusing Distance: 0.38 m (1.25 ft)
- Maximum Magnification: 0.21 x (at 70 mm)
Construction:
- Lens Groups: 13
- Lens Elements: 18
- No. of Diaphragm Blades: 9 (circular aperture)
Physical:
- Lens Mount Type: Canon EF
- Filter Diameter: 82 mm
- Maximum Diameter x Length: 88.5 x 113 mm (3.5 x 4.4 in)
- Weight: 805 g (28.4 oz)
Accessories:
- Lens Cap: E-82U / E-82 II
- Lens Hood: EW-88C
- Case: LP1219
- Magnification - Extension Tube EF12 II: 0.63 - 0.18
- Magnification - Extension Tube EF25 II: 0.74 - 0.41
Source: Canon Camera Museum