A pair of spectacles might easily afford good evidence for identification; that I perceived clearly enough.

Not a ready-made pair, picked up casually at a shop, but a pair constructed by a skilled optician to remedy a particular defect of vision and to fit a particular face.

And such were the spectacles before me.

The build of the frames was peculiar; the existence of a cylindrical lens--which I could easily make out from the remaining fragments--showed that one glass had been cut to a prescribed shape and almost certainly ground to a particular formula, and also that the distance between centres must have been carefully secured.

Hence these spectacles had an individual character.