The adjustable stoptail is currently out of stock, but should be back online in the near future.
The straight stoptail works great for 9 or 10 gauge strings and Paul feels the solid mass sounds better than the adjustable version.
The bridge is unplated, polished aluminum. It is what we used for all guitars receiving Nickel hardware. in 2008 we stopped plating the bridge because Paul (yeah, that guy) feels the bridge sounds better without the plating. Some people accused us of trying to cheapen out by doing away with the plating, but the bridges actually require more work and cost more money without the plating. With plating it's possible to hide minor imperfections. When naked metal is being used, there isn't any plating to hide behind.