This is separate but sort of related to installing  swell shades. We
have not found a serial number anywhere, so we have not found a serial
number anywhere which would let us date the machine. Our  W153 does not
have 4 in 1 valves, nor does it have individual unit valves. It has a
player piano style air chest and pneumatics that push down the vales to
sound the notes. What does that tell about the probable build date?