A flat, double bar, made of brass, which terminates in a triangular point at one end. A steel rod with a central crevice is fixed to this point.
The surface of the bar is marked with lines, parallel to its ends, and marked 1 to 15, 15 to 1, with intervals that diminish towards the centre of the bar.
The bar crosses a disc which has a limb graduated from 2 to 12, repeated twice, with an oval window directed towards the opposite end. A compass with a magnetic needle, a glass cover, and a pointer which is free to move over the graduated circumference is located at the centre of the disc.
The disc is followed by a sundial, engraved onto the same bar, with the hours numbered 4 to 12, 1 to 8. Finally, pivoted to the opposite end, which is flat and moulded, is a pierced, reclining plumb-line, the point of which can be placed inside the window of the disc. The weight fixed to this end of the line moves across the graduated arc of the pendulum, with divisions 2 to 0 to 2.
A moulded cursor, with a stopping-nut, slides along the bar. The abbreviation 'I B F' is inscribed on the cursor. Two graduated rods, divided from 1 to 4, are screwed to the sides of the cursor. One bears the inscription 'Weiner', the other 'Romer'. A the ends of these rods two other moulded rods are fixed. Each of these is pointed and was originally furnished with a steel hook, to be inserted into the bar with a crevice (one of the hooks is now missing).
The abbreviation can be interpreted as Iost Burgi Fecit. The accurate engravings allow this attribution to be made on the basis of comparison with similar instruments made by the same craftsman.
See M. Miniati, Museo di Storia della scienza: Catalago (Florence, 1991), p. 30.