Yesterday I was beginning to leather the valves for my "D".  (I am
pirating metal parts from a late Steinway aluminum cross-valve stack.)
Over the years I have noticed at least four distinct varieties of pins
in these valves, and there may be more.  I wouldn't be surprised if one
of the greats (Morgan, Brougher, etc.) have written extensively on this
subject but maybe its still news to some.

Three of the four varieties have crimping on the shaft to hold the valve
button in place.  The fourth has both the crimping and a collar to keep
the button from loosening and migrating down the shaft.  The valve
stems from my Steinway stack did not have collars.

Yesterday, I came across one of those valve buttons (out of 88) that
was loose -- just slightly.  I had presumed that the stems with the
collars were reserved for Steinways, as the button takes a small inset
hole to be drilled just the right depth into each button; expensive!

I've only seen collared stems before Steinways and early Webers.
Usually Stecks, etc., have the other versions: some of them have
chopped-off tops, some have rounded tops, but no collars.  I have yet
to see a collared stem that did not have a round top.

What does this have to do with playing weakly?  Perhaps if there are
a number of buttons that had loosened and migrated down the stems (during
playing loud) they might not be rising far enough to seal properly).

For my "D" I wanted aluminum cross valves, and collared stems.  I have
several sets of old style (plated, not aluminum) cross valves I'd gladly
trade for a set of collared stems.  Any takers?

Bruce Grimes