Keith,

That is charcoal bluing.

Stanton,

The lock plate has an extension on it that has the hole for the lock screw. If you can magnify the picture you can see where the joint takes a right hand turn at seven o'clock into the circle around the screw head. If you look at ten o'clock on the trim you can see the joint coming from under the hammer. The circular joint is masked by the engraving. It is a semi island lock.

I hope that helps. Thanks for the compliment.