Crankset is FC-6500 - Ultegra 9-speed. I've measured the crank length (center to center) on these and although I'm eyeballing the centers, I'm getting about 172.5 mm. Stamped on the inside of each crank on the shaft side of the pedal hole is "170". There's other stamping, but no part numbers that I can see.
Are these 170 mm cranks? Would a 172.5 mm arm be stamped "172.5"?