For many months, I had no idea where this was used, Then one night, I was watching the episode "The Minds Eye", in which Geordi is kidnapped by the Romulans, brainwashed and ordered to kill a Klingon. And there it was, being used by Geordi to carry some Isolinear chips when he was trying to cover his tracks.
If that wasn't good enough, I was then made aware of other appearances throughout TNG, by Star Trek God, Jorg, over at the Star Trek Prop Forum (See links). I owe him a lot for digging these out for me!!!
So, what turned out to be an unknown prop, turned out to be a great prop used in several episodes. I lucked out on this prop, got it for a great price, and will remain in my collection for some time to come.