I have to hold my hands up on this one.
I've never used it or one like it.
And I don't 100% know what it is.
I've tried a reverse google image search with no success.
It just happens to be something I acquired as part of a larger transaction.
But I'll sell it happily as it is just sitting in a drawer taking up space.https://i.imgur.com/J0VShht.jpg
I'm going to say £50 (yeah right) ... and make me an offer!!