To answer the question about marking, I do not think there is a specific one.
I doubt if you will find anything powered purly by SELV, as has been stated previously if it has a seperate charger/power supply then the whole system must be tested as a mains powered unit to class I or II as appropriate.
If it is purely battery powered with no direct or indirect mains connection then that is obvious.
The B, BF, CF markings are the same what ever class the equipment is.
Robert
