An unusual slider...any ideas?

[Photomicro]

I found this recently, in a box of 'junk' and it looks like some sort of slider. However, there is no makers name, and i am unsure if it is for sub-stage use, or above the objective.

I hope the pictures show that there is a small lens behind the slit.

Nicely made, it would be nice to get it in the hands of someone with the right part(s) to use it with.

Mike