These knives are known for being very robust, over-built and often referred to as "tanks".
The R-30 was one of the early models made by this company, featuring a 3.5" 440-C stainless steel blade, double hollow-grind and a rosewood handle. The original Rigid knife company was started by Bill Duff and Don Colum and ran from the early 70's through the mid 80's.
Contact me if you have questions and thanks for looking.