OK, so since I'm probably the only customer in the world that owns both
a CarolBrass horn (658) and 2 Harrelson Bravura's, I happened to discover something quite interesting.
The standard valve block (non-upgrade) used by Harrelson is identical to
the valve block used on my Carol Brass 658.
I noticed it this morning that from the outside my CB658 and my Bravura C trumpet looked identical in the valve block. I took out the valves and was amazed to see that the pistons are identical down to the font and location used to indicate the valve number.
I swapped the piston between the two horns and they are perfect matches.
Apparently the parent company, Hoxon Gakki, has been supplying Harrelson with valve blocks since early 2009.