Ifyou have an old slide rule lying around that you'd like some cash for , a description of the bulleted items below and I'll gladly quote a price and give you an independent site URL to verify it. It could be worth from US$35 to $135 or more. If you have access to a decent digital camera or can scan it, include a good image of the stick and any accessories.
Factors affecting value include:
Right now, I'm looking for and prefer the pocket variety (5-in. or so) and circular types and prefer K&E, Pickett, and Post manufacture (Lietz/Pickett and Concise circulars).