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Diskussion:Washington-Betonrechner FER H-39
Hello, Ferrero/Sabatini relationship in not completely clear. Some Fer slide rules seems clearly "sons" of Washington slide rules.
Pastore in is 
book describes:
- Sistema Washington (Ferrero n° H-39) pag. 409
- Sistema Ferrero (Ferrero n° R-8) pag. 439
See also Patent:IT354168 and Patent:IT348024, released in the same year. Patent reported on slide rule (Brev. It. 1680) is very early. I suppose near 1910 and i had not (until now) the possibility to explore patents of these years. :-(
I'm quite sure that Ferrero produced last versions of Sabatini rules, but i seen on eBay a rule labeled Sabatini (not Ferrero). It was very similar to http://www.lombardiabeniculturali.it/scienza-tecnologia/schede/ST120-00195/ Celli 11:12, 25. Ago 2011 (CEST)
I suppose to have now an almost-complete framework for Washington-Betonrechner history.
- First Sabatini device was patented in 1925 (Patent:IT236298). In Patent:GB265752 you can see the GB registration (1927) of original Italian patent. It had two series of concentric rings linked troughs gears. This model is very rare, i know just two specimens: one in Franco Soresini's collection, one here. The second one has serial number 227.
- After few years, Sabatini patented a new calculator, who is scarce, but not so rare. Related patents are Patent:IT272159 and Patent:GB331819. Now all rings are concentric. Both machines (first and second type) was produced directly by Sabatini himself.
- Finally, i suppose after WW2, the Ferrero company acquired patents and produced a "restyled" and "compact" version, the Fer H-39N. I suppose that the label "Brev. Ital. N.1680" refers to a "Brevetto italiano di modello" a sort of "registered model", not to a "brevetto d'invenzione"(= patent) Celli 12:14, 2. Apr 2012 (CEST)