This small parallel rule is of the type that
one usually finds in small navigational or engineering drafting kits. Not marked
by a maker, this one it is stamped by a one-time owner
“I. S. Biddulph” / “C. C. E.”
There is a small town in Staffordshire, England called Biddulph and an extant genealogy of people with that surname. Perhaps a little sleuthing is in order. The rule is Fine.