Slide rule for interest calculations
1824
Merchants' Graphic Profit Finder, mid 20th century
1950-1970
Arithmetical medal and numerical pocket piece
1753
'Supra Bareme', ready reckoner, c 1925.
circa 1925
McFarlane calculating cylinder, c.1835.
circa 1835
Two gilt bronze arithmetical medals, c.1753
1750-1755
One of Two gilt bronze arithmetical medals, c.1753
1750-1755
One ot two gilt bronze arithmetical medals, c.1753
1750-1755