The Peak Lupe comes with limited documentation:
The Lupe comes with five inserts that assist in measurement.
The inserts are held in with a metal end-cap that screws into the threaded plastic.
The inserts are well designed and quite useful.
The detailing on the inserts is crisp and clear.
The original case was flimsy and difficult to open. I elected to replace it with a Pelican 1030 Micro Case that holds the lens and the inserts safely.
This is a very handy loop. I bought it used for a reasonable price and I have been quite pleased with its performance. Many people I work with borrow it, and I am always corralling it back to my desk. There is room for improvement (built in lighting, better materials, high quality components), however, none of these upgrades would likely be worth the corresponding increase in price.