One well known example is the viewmaster viewer and reels of images.
Another example is the dual image stereoscope of old, that views two printed images.
The anaglyphs are single pictures made from combining a left and right image.
Red or blue components of each image are removed and the remaining colors combined.
The resulting image retains the depth detail, but must be viewed through glasses.
The anaglyph image therefore has color distortion through the red/blue glasses.
This means that the anaglyphs are somewhat difficult to view to begin with.
The amazing human brain interprets the images and gives us the depth sensation.
Most anaglyphs are to be viewed with the RED LENS over your LEFT EYE.
When using the paper glasses, do not warp or pull the glasses around your eyes.
It is best if the glasses and acetate "lenses" are straight and not wrinkled.
If you normally wear eyeglasses or reading glasses, you need to wear them also.
Hold the paper glasses in front of your normal glasses to view anaglyphs correctly.
The paper frames will absorb oil and moisture from your face and get softened.
If you choose to wear them on your face, put scotch tape around the nose and ear tabs.
You may want to place and remove the glasses over your eyes while viewing 3D pictures.
Some choose to cut the side/ear pieces off, and staple them back on like opera glasses.
If you are right handed you probably will want the "holder" pieces on the left side.
This allows you to easily place and remove them from in front of your eyes.
It also prevents the tendency to pull them close and wrap them around your eyes.
Attaching the pieces opposite your working hand leaves it free to click on web selections.
There are hundreds of web sites that have anaglyphs from long past and current time.
Search for the keywords 3D, anaglyphs, stereo pictures, and you will find many to view.
3D pictures have come and gone over the years both as a novelty and for serious work.
The most recent use is by NASA on the Mars rover, over 100 million miles away!
They chose to equip the cameras as stereo cameras so the scientist's see depth detail.
You can search the NASA web sites for 3D, or anaglyphs and find amazing pictures.