HP15c is a web application for consulting the classic HP15C desk calculator in a browser. It's self contained and can be installed as persistent web app and will run with no network connection.
This app is a new front end for Greg Hewgill's HP15C simulator. It is built as a Progressive Web App using tools from Google's Polymer Project. The source is available at github. The manual for the hp 15c is available from Hewlitt Packard, but be aware that it is a 288 page pdf.