Plastic Retaining Clip for windows of unknown manufacture

Customer brought one of these retaining clips in today (pictured) says he need maybe ten or twelve? May be able to provide manufacturer details if he can find a lable (on others yet to be cleaned) that's not so faded as to be illegible.
I thought at first it was some kind of drawer support; instead it's used to secure plastic framed windows somehow. I know I've never seen anything like these for exterior or interior use. Plastic just doesn't hold up over the years. The one pictured has a crack on one side of the screw slot. You just might be able to discern that in the upper image (of three in one pic) if you look closely at its lower half, below the screw slot.

I'll pass the specs on to my customer, thanks! I was so frayed @ work when he stopped in it was all I could to to grab some pics of his sample to send you, I failed to get some dimensions... my bad!
My SWAG is that these'll work! What's next I'll leave up to him!!