I used to own one of those Yamaha's, mine was so old it had a yellow brass bell.
Anyhow, I loved it. It played great and was loud with controlled edge in the low register. However it sounded tight enough to play 4th T-bone in some Ellington (and other old standards where the forth bone never leaves the staff) charts.
IMO, thes play about as close to a good combo of the better parts of the Holton and Conn Bass Trombones from earlier days. I always found it strange that this horn consistently outsold all other Yamaha bass trombones. It is a shame they dumped it.
You'll enjoy it, Joe. You might even end up keeping it for a long while.
I used to own one of these before I got into independent valves. Also before the independent fingering for stacked valves. I loved the sound and feel. If its going to be in the shop during the holiday season, I would like to see the finished product.