file signature for files that make up postgres database

Hi I am trying to recover a postgres database from a ext3 partition
that the filesystem has become corrupt and lost files.  Can anybody
tell me what are the file signatures for the files that comprise a
postgres database?

Anybody know of any tools that can detect and recover postgres files
from an EXT3 partition?  I see that photorec is supposed to be able to
recognize mysql database files.

Thanks,

Lee