The pair of magnets presented here consists of two identical tempered steel rods (29 x 2.5 x 0.7 cm) kept in a wooden box signed on the inside by the manufacturer.
The two magnets bear the letters N and S to indicate the poles; the same letters are printed inside the box to ensure that they are kept in the correct position between the iron clamps.
Daguin (1878), T. III, p. 46
De La Rive (1854), T. I, p. 202
Perucca (1949), Vol. II, p. 465