Dave Wilcox asks, "I have a Nelson-Wiggen Style 3 with xylophone
serial no. 100911.  What pitch should it be tuned to, A435 or A440?"

Unless you want to go to a whole lot of trouble the answer is
easy -- tune the piano to the xylophone.  The only reason absolute
pitch might matter is if you need to be in tune with other
instruments that would be even harder to adjust (or perhaps to play
along with a concert pianist with perfect pitch and a big ego).

Re-tuning a xylophone to match an arbitrary pitch standard in
a standalone instrument is a lot of work and will make essentially
no difference to a listener at the end of the day.

Cheers,
Roger Wiegand
http://www.carouselorgan.com/