There are four, more or less independent, topics on this website.  Click on one that interests you.

Slide Rule Trading Company:  Buys and sell slide rules, slide rule repair parts, cases, advice on repairs, etc.

Hemmi Catalogue Raisonne:  Description of every numbered-model slide rule made by Hemmi Slide Rule Company of Tokyo,  

Hemmi Catalogue II:  Description of every Hemmi slide rule that did not have a model number.

POST Slide Rule Cross Reference:  Every slide rule sold by the Frederick Post Company of Chicago starting in 1903.  

Don't worry if you get a "not secure" message when you log onto these websites.  "Not secure" means I don't have an "SSL Certificate" and I cannot guarantee that information you enter will not be read by some diabolical hacker.  But you cannot enter information into any of these websites.  None of these websites asks for information and there's no place to enter any even if you want to.  If you want to ask or tell me something, do it by email and save me $239 per year.