DescriptionPhiladelphia rod micrometer target, 81 0239 (formerly 6210T?), made by Keuffel & Esser Co., no date, circa 1960-1975. Oval metal plate painted white with red quadrants, 6" wide x 5" high; vernier steel scale; clamp screw and micrometer adjustment handle. Designed for use on Metagrad Philadelphia 1610 or later leveling rods used by surveyors and engineers. The oval plate is cast with the K&E logo and name in raised letters on the back. Above these letters is the model number ink stamped in black. From 1956-1962, K&E changed over from its traditional basic product number of a four digit code (often supplemented by a letter or letters and/or a hyphenated number) to a new six digit product code. From 1956 onward (for an indefinite period), the new number and old number were often published on product sheets, labels, etc. A catalogue depicting this item number is not available at present; a reference image from the 42nd edition catalogue of 1954 showing the same item as 6210T is shown. K+E main office and factories were in Hoboken up to December 1968.