An antique dealer friend in Philly went to the Free Library to research a
piece in auction catalogs, and was referred to an online database.  He was
ranting about how he'd allotted an entire day to the process, but only spent
a few hours, including lots of playing around on the system.  If the search
engines yield nothing, try the reference desk at the Free Library of
Philadelphia (Main branch is something like 20th & Ben Franklin Parkway).
 Sorry, I don't have the tel#

Adam Zuckerman
Curator
Worcester Historical museum