B. Wilson says:

Initially great, but some long-term problems High precision sighting compass with a sighting clinometer, built into a very sturdy aluminum base. The sighting lenses are resesses so they won’t get scratched, but they will gather dust. Fortunately, the dust is easily removed with a cotton swab, and won’t interfere with observations if it’s there.You use this by holding it to your eye, with both eyes open. You will see the scene in front of you, and also, in the eye looking into the compass, the lubber line and magnified compass…