I'm rebuilding a George Steck Duo-Art grand.  I didn't find a crash
valve primary in its expression box, as I have seen in all Duo-Art
grands and related literature.  But there is a pallet valve actuated
by Theme level 15, and a nipple in the expression box (no tube in it),
that should operate the internal crash valve.

Where is the primary valve?  It's not simply missing.  There is no
empty screw hole anywhere to hold it.

Leonardo Forti
Rome, Italy