What Is This?

[Sarcophilus Harrisii]

Looking at the very fine adjustments built into it, I suspect it's some type of close focusing accessory. But for what camera, lens, or application, I have no idea. It came in a lot of miscellaneous Leitz rangefinder and other photographic equipment. Made by Tasco, according to the name on the reverse, but no description or other clues are on its box. Any information gratefully received.
Cheers,
Brett

 

[Dralowid]

Tasco make (or made) binoculars and gun sights etc, someone will know...

 

[Arthur]

It is intended for use in photomicrography; i.e. for maneuvering a microscope slide about. The user would be able to find again a particular finding, or feature, using the numbers.

 

[andrewmore]

Not just for photomicroscopy, but microscopy in general. Things like this are often found on higher-end microscopes as a built-in (or easily detachable) feature.

Regards

Andrew More

 

[rfaspen]

Slide positioning apparatus of a microscope stage. I might grab a photo of one of mine if I make it into the lab today...

 

[Sarcophilus Harrisii]

Thanks very much, everyone. Much appreciated. Wouldn't have worked that out myself. Here's a search result I found with your suggestions (an unrelated eBay listing with images and description).
https://www.ebay.com/itm/Vintage-Tasco-Mechanical-Slide-Holder-Microscope-Slide-Kit/293216001649

Thanks again!
Brett