Stanley 64R Engineers, precision, rigid steel, rustless rule, metric/imperial on 2 sides, 4 edges.

Imperial side is graduated to 16ths, 32nds, 64ths, 10ths, 20ths, 50ths, 100ths.

Metric side is graduated to 0.5 mm.
Class 1 rule.

Length. 300mm (12 in)
Width 25 mm
Thickness 1 mm