Janssen serial numbers - help

[Clyde Hollinger]

Friends,

I routinely look up the age of pianos I service and record the info with
my service records.  Yesterday I serviced  a Janssen console with
serial  #305198.  My Pierce atlas has serial numbers up to 1960
(150036), then skips to 1970 (500001), when Charles Walter purchased
Janssen.

Can anyone tell me where to find the age of Janssens made between 1960
and 1970?  And who made them?  The tone is pretty rotten in the bass.

Regards,
Clyde Hollinger, RPT