This is what I got from customerservice@gloomis.com:
The first letters are the type of rod it is, STR “steelhead rod” The next three numbers are the rods length in inches 144” which would be 9’6” Then the last number five will be the power rating of the rod. A three in this series would mean that the line rating will be 6-12lbs. All together you get our description STR1143C
Jon Bissell
Fly Fishing Tech.
1-800-662-8818 X287
Looks like he right about the numbers, but his calculations are wrong. 144" is 12', and 126" is 10'6".
For the power rating. I know the STR1266C is rated for 10-40 line and 2-8 oz. lure, while the SAR1265C is rated the SAME.
So the complete rule is:
STR, SAR: STeelhead Rod, Samlon Rod
144, 126: 12', 10'6" length
5,6: power (higher number means more power)
C,S: Casting, Spinning
Also read the rating as different power numbers can have the same ratings and vice versa.