A computing instrument, comprising a circular brass plate (243mm diameter) with several scales. At the centre is a calibrated knob/dial (40mm diameter), marked 'C' in the centre and with a scale running 0,+1 to+ 9 then 1 to 6 , and 0, -1,-2,-3,-4,-6 . Beneath the knob, the base plate is inscribed, 'NYSTROM'S CALCULATOR', 'PATENTED MARCH 4. 1851', 'MADE BY W.J. YOUNG' and 'No.758'.

From the central boss, two radial arms carry scales marked 'A' and 'B' (at end of arm). A is engraved 'Points Dep cos 0,1,2,3,4,5,6,' coincident with '6,5,4,3,2,1,0', and 'sin b 9,8,7,6,5,4,3,2,1,0' coincident with '9,8,7,6,5,4,3,2,1,0'. The fiducial edge can be read against the scales on the large dial. 'B' is engraved 'Points', 'Dep' and 'cos 0,1,2,3,4,5,6', coincident with '6,5,4,3,2,1,0'
and 'sin b 0,1,2,3,4,5,6,7,8,9', coincident with '9,8,7,6,5,4,3,2,1,0’.

The scales on the base plate are:
1) Circles (from centre) 0 -6 anti-clockwise, divided into quarters
2) Similarly 1-8
3) Similarly 1-8, also a degree scale and curvilinear diagonal scales for fine reading.
4) Scaled 0 – 9, zero, then 1 -10 zero again.
5) The outer scale is marked 1 – 9, then 9 again.
The scales appear to be duplicated, corresponding to the two radial arms.