There are other types of compass but all should have at least these minimum features ( a pointer and a graduated dial)

A compass is a delicate and fragile device : do not drop it or bump it, keep it away from the sand. A case to protect it is more than welcome when you don’t use it.

A compass finds a direction thanks to the earth’s magnetic field. If there’s another magnetic field not far your measures will be wrong. If you do not want to have a bad surprise you should avoid :

• A metallic weight (the bonnet of a car is very useful to lay out a map but absolutely incompatible with compass use !)
• Magnets (On phones for example),
• Voltage transformers
• Power lines
• Ferruginous grounds