This is a fully working Fowler's Twelve Ten calculator in very good condition, dating to the 1930’s or 1940’s. Introduced in 1936, this particular calculator was primarily designed for Architects, Surveyors, Builders and Craftsmen, and is one of the more hard to find models with the chrome back plate.

It was known as the 12-10 because it includes scales to convert twelfths to tens, yards to metres, lbs to kgs, inches to centimetres etc., and the two milled adjusting knobs rotate the dial and cursor.

The scales are very clean and the dial reads FOWLER’S “TWELVE – TEN" PATENT CALCULATOR, Fowler & Co Manchester, and is accompanied by a modern reprinted copy of the 64 page instruction booklet.

In excellent cosmetic condition, the chrome back plate is free of any dents, with no tarnish or chrome loss and the glass front cover is also undamaged.

The calculator measures 85mm in diameter, and weighs 300 grams in its leather case which is also in very good condition.