What is a "Spoonplug (R)" ?

[NoMuskyJoe]

A "Spoonplug (R)" is mentioned on pages 10, 11, 12/Vol 5 of the Buck Perry Guidelines for Fishing Success and was wondering what the "(R)" is for ? I have heard that there was a "floating" and a "weedless" Spoonplug, but are no longer made. Thanks for your help with this.

[jwt]

(R) is the symbol for registered trademark.