Slide viewer I think assuming size

It's a

This. My grandfather had one.

Fixed focal length that is ideal for examining stamps.

This is correct. Before computers we used them in graphic design to look for scratches on our galleys before we sent them off to the camera.

That’s called a printer’s loupe or a linen tester. It is a folding pocket magnifier that focuses at the square hole.

For inspecting lithograph plates, given the labeling on the front of it. Pretty nifty little gadget.

This is wicked cool! My collapsible is plastic, I love this.

We use to use them to do press checks to see how the registration lined up. Color photos in newspapers and magazines are made up of four colors plates, yellow, magenta, cyan and black. You'd use this to make sure all four plates were aligned and not out of registration which makes the images look blurry.

thank you all it is solved!

plusminus20

That is really cool. I didn't know those were a thing. I almost chimed in saying it looked a lot like a

It's for looking at print quality. Lithography is a form of printing - the printer would place this on the finished print to see if the colours are lined up, to look for damage to the printing plate, or just to check the quality.

There are ones that are a perfect 1" square for counting stitches in fabric. Ex. thread count in your bed sheets.

Viewer for slides or contact sheets, basically it would magnify since both were tiny. I’m sure most people today can’t understand that you can’t just use your fingers to expand the image

My dad used this to see and take out my splinters