Piece of Rhynie chert. Chert is a hard silica-rich rock. Rhynie chert, over 400-412 million years old) was first discovered by Dr William Mackie in 1912.
Small wooden box with 2 brass terminals on top and a brass plate which reads "1 OHM, Univ. Abdn., Nat. Phil." Embossed into the wood is "HARVEY & PEAK, LONDON".
2 terminals mounted either end of a metal beam with another 2 terminals at one corner of metal squares, all mounted on top of a wooden base. Engraved on the side is "15" and "AMP" and the number "106888". Holes through metal and wood at either end.
One of two metal resistance boxes with 4 plastic dials for changing the resistance and 3 screw connectors. In white lettering there is an inscription on a metal plate.