Hemmi model 301 (Slide Rule) and 301A ("Special Quadratic Scale Attachment")
This slide rule first appeared in the 1960 General Catalog and last appeared in 1966 but was probably available for a few years after 1966. It had four three-line cursors.
|1960 Frederick Post General Catalog, Pages 82-83
Date code "HK" (November 1957)