Filotecnica Model 201 Back-Light Screen Projection Slide Rule, I

In the early 1950s the company Filotecnica Salmoiraghi, well known for its precision equipment, developed a slide rule that projected the scales onto a backlit screen from the patents of Abeille and Aquilecchia. This solution allowed a very compact device to have the same precision as a traditional slide rule of 2.5 meters. With logarithmic calculators, precision is in fact proportional to length. - The goal was to market a logarithmic calculator cheaper than an electro-mechanical calculator. This aim was only partially achieved: the device is in fact very precise but was still too expensive. At the time of production, it sold for around the same price as a good motorcycle, and was the equivalent of two months’ average salary. It proved too expensive for individual professionals, while companies preferred to buy the more expensive, but tried and tested, Olivetti Tetractys. According to an article published in the journal of the Oughtred Society, the project was discontinued and only five units were built. - This example is one of the three known survivors, a fourth is in irreparable condition and nothing is known about the fifth. This unit is in excellent condition, complete with instructions in Italian and a probably non-factory leather case. The serial no. 45605 is typical of the factory, which numbered products in order of exit from the production line and not according to the series or model. No. 45605 appears among the four reported surviving instruments on the website http:/Iwvwv.rechnerlexikon.de. This unit appears to have been delivered to the communications company Telettra (one of the most important at the time) in 1955 but shows virtually no signs of use. Advertising for this calculator appears in the Filotecnica catalogs only in the years 1954 and 1955. Filotenica Salmoiraghi, founded in 1865 by lgnazio Porro - the inventor of prismatic binoculars, was the main Italian factory of optical, nautical, measurement and precision instruments for the best part of a century.

布雷克拍品等级是为了方便竞买人判断拍卖品的成色而设置的。布雷克等级用1到6级来标注外观和功能的成色，(从非常好到非常差)。 在目录图册里用括号里的2个数字来表示，前一个数字表示外观成色的级别，后一个数字表示功能成色的级别。如(3/2)表示外观成色是3(满意的)，功能成色2(好)。 成色 定义参照下列标准： 1 - 非常好 (未使用过，没有使用痕迹) 2 - 好 (新，极少的使用痕迹) 3 - 满意的 (普通的使用痕迹) 4 - 及格的 (明显的使用痕迹，某个非主要部件是后配的) 5 - 有缺陷的 (极明显的使用痕迹, 某个主要部件是后配的，功能上有缺陷，需要修理) 6 - 非常差 (严重破损, 缺少重要部件)