The Granger sounds very interesting ... assuming it is tight and straight with the original markings, it may have excellent value. However, I defer to Len Codella who I regard as a true expert on bamboo rods, their makers, and, of course, their value. He's busy but try him at email@example.com
or call 1-352-637-5454.
I'll bet it is a 5-weight. There was a time when makers gave the length and weight and left matching line to the fly fisher. A.J. McClane did a piece years ago and classified rod in groups: 7.5 to 8-feet, 3.5 to 4.5 ounces; 8.5 to 9-feet, 4.5 to 5.25 ounces; 9-feet, 5.5 to 6.5 ounces; an 9 to 9.5-feet, 6.5 to 7.5 ounces. If your Granger falls into the first category a 5-weight should work.
Best of Luck,