Vintage Slide Rules: Simplon Bilateral & Unique Universal I. Drague Brothers Ltd. of Halifax , incorporated in 1912, were the manufacturers of a wide range of technical instruments, from crystal radio sets to drafting equipment. Most, if not all of their output bore the trade name ‘Simplon’. Their bilateral Log-Log slide rule, patented in 1934, was no exception. Described as a 10 inch rule (it’s actually 12¾” overall – or am I missing something here?), it was double sided and made of plastic faced mahogany. To allow for the use of the duplex scales, there are two cursor grooves along each edge of the rule, so that the cursor can be removed and put on the other side to use the scales on the reverse. The scales are: LU,A{B,C1,C}D,LL//A,S,L,T,D. The example on offer here dates from the 1960s and comes complete with the original (and now somewhat tatty and fragile) instructions and a dark blue card case (which is – incorrectly – labelled as containing a Simplon Primary rule). The rule itself is in excellent condition. The second slide rule on offer here was manufactured by Unique. The company, which was founded in Brighton in 1920 by one Burns Snodgrass (author of Teach Yourself the Slide Rule ), was well known for its range of wood slide rules with celluloid covered paper scales. These were cheap and popular. Three different Universal