Phil - Sorry I do not know what the extra letters designate.... Your "R" above the serial number is just one example of extra letters. There are letters after the numbers, and below the numbers on various Bear Bows.
We may have to do an actual study of these extra letters, something like the study we just got started on about the 1959 Kodiak Specials on another thread.
Give me another day or two to try to get others to help with a first draft of the next group of Grizzly bows to date...
Brad - Your Second bow #25912 red glass is really a single shelf 1953 with a second shelf added or wedged inside the leather grip. I've seen this on several bows including Bear Grumleys.
The true dual shelf has both shelves cut into the riser wood, not added inside the leather grip like yours... Thanks for posting the photographs
Just modified the dating system to reflect these changes... check it out now... there may be a clearer way to word the text...