1. The Versalog Slide Rule Instructions,1951, 115 pages , pub Frederick Post Company £20 (Cover spine detached)
2. The Mannheim Slide Rule, complete manual, William Cox, 48 pages paper covers, 1917 (good condition) £25
3. The Slide Rule, C. N. Pickworth 20th Edition, 1935. (Reasonable condition) £20
4. Instructions for the Use of A. W. Fabers Improved Calculating Rule, by C. N. Pickworth, 14 folding sheets of scales, (Cover rough but intact) uncommon, undated probably 1910. £50
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