Numbers on BR-9000 brakes?
 

Not an earth-shattering question, but I just noticed on the inside bottom of the brake pad holders near the "wing" and the wear-indicator screw, there is a number. On my Dura-Ace 9000 brakes, three of the four holders are marked with a "3" and one is marked with a "2". All four holders look and measure identical.

I thought I understood the Shimano date code strategy (and I see the codes on the body of the brakes), but what are these numbers and why is one different?

There is no 'wear indicator screw'. The numbers? Who knows.

I guess those "screws," Shimano part #Y8FA16000, are officially part of their tire-guides. I've seen plenty of posts quoting Shimano's own words describing them as "wear indicators" useful to prevent damage when using deep-section carbon rims. They are certainly there on both my DA 7900 and DA 9000 brakes.

But I agree, who knows what those "3" and "2" marking on the pad holders are.

Probably just some type of identification mark.
If they start getting defective pads with a "3", they know they have to fix machine "3".

Thanks. The idea of some sort of manufacturing identification mark seems like a plausible explanation.