I can do a little research while in recovery. Harvey, according to Goins' Encyclopedia of Cutlery Markings (1998), the company was founded "in 1908 by Ernest Enderes in Littleport, Iowa. In 1916, they moved to Albert Lea, Minnesota. Enderes had three factories in Albert Lea, each making small tools and cutlery.
In 1926, Enderes sold his Albert Lea operation to E. J. Pihl. Enderes then moved to Guttenberg, Iowa and started to manufacture tools under the 'Original Enderes' name. The cutlery with the 'Guttenberg Iowa' marking were made by other firms on contract."
According to Goins, your knife, with the ENDERES in a rectangle, was made by Enderes in Albert Lea between 1916-1926.
- Stuart