huw:

"...clearly intended for double sided operation..."

I see that the bit is symmetrical, but only along the length of the post; one side of the bit is relieved nearest the post, and on both ends...but not on the other side. I'm confused (obviously) about what double sided operation means: is it that the key will function (open or close) the lock when turned either way?

Then, as I easily accept your argument that the key was not a 'universal' blank, I have to ask what purpose the apparent capped barrel serves: why the tightly capped hole? The cap cannot be easily removed; I haven't tried very hard, but fingers won't do the trick. Needing some tool for cap removal when the key was to be inserted, not to mention the potential for loss of such a small item...seems a clumsy stretch, to me.

Also, can you (or others) estimate a value for this key?

Thank you for the anatomy lesson, and your continued interest! wlw