There are a number of wonderful sites devoted to HP history on the Web. The people who created these sites have worked hard for little or no reward other than the appreciation of their visitors and they have all been a tremedous help to me in my efforts. Take a look at these sites and let them know you appreciate their work:
HP Memory - A comprehensive site of HP products and documents going back to the dawn of time. Beautifully built by the elegant and knowledgeable Marc Mislanghe, who passed away in 2014.
The HP Computer Museum - Located in Melbourne, Australia. Founded by Jon Johnston who passed away in 2016.
Museum of HP Calculators - A haven for calculator collectors, especially for handheld calculator enthusiasts. Built by David G. Hicks.
The Old Calculator Museum - Not specifically an HP-only site, but a real treasure trove of calculator-related lore. Built by Rick Bensene.
Electronic Calculator History and Technology Museum - Alex Knight’s comprehensive calculator site.
The HP 9845 Project - Well done site on the HP 9825’s big brother. Created in 2008 by Ansgar Kuckes, Berlin.