Description
Engineer’s two fold box wood Railway Timber Content slide rule to Burt’s provisional patent No 3551 for railway weight tables (c.1893). Used for calculating railway weights.
For a short description of the item see: https://static1.squarespace.com/static/54ec9b40e4b02904f4e09b74/t/567fd89a1c1210eb4f678c7b/1451219098947/SIS_Bulletin_003.pdf.