Strange... on the Brooks site, it looks like the the "ATB/Trekking" versions have chromed rivets, while the "Road/MTB" have copper. You can get a B17 std in either line... is there a difference besides the colour of the rivets?
Soma Rush, Fuji Cross, Raleigh Technium Mtn Bike, Ross 10 speed with Shimano 600.
the standard B-17, and B-17n come with steel. The B-17 specail comes with copper. The Ti-rail models seem to come in copper. Basically, I think the least expensive models use steel machine set rivets, the more expensive use copper hand hammered rivets.