Thank you for for the kind words.
Ethelred - Please feel free!
Vagabond - It's not strictly covered in the rules. I just say that they emanate a "magical aura" and they will need to do a bit of research/experimenting to work out what the objects do. Effectively, I tell the players what they are, but only after the scenario is finished and their PCs have some time to spend investigating properly, consulting magical tomes etc.
blacksoilbill - It's a 3x3 feet table.