A set prisms in a brass frame that allows the prisms to be folded flat against each other. The set consists of three single prisms, two of crown glass, one of flint glass, which can be combined in different ways. It was designed to demonstrate the working and effectiveness of the achromatic objective lens first patented by John Dollond, which combined flint and crown-glass elements into a single lens. The set is held in a fitted wooden case that is covered in rayskin.

Evidence that these sets were bought and sold in the eighteenth century comes from a number of different sources. A portrait of John Dollond (ZBA0725, PAJ3274) shows him holding a set of prisms. The auction catalogue of the instrument cabinet sold after the death of Petrus van Musschenbroek (1692-1761), a professor in Leiden, described in one lot 'a prism made up of 3 prisms composed of different glass set in copper, serving to clarify the construction of Doullont's telescopes'. Likewise, in 1777 the Danish astronomer Thomass Bugge bought a triple prism from the London instrument maker Addison Smith.