[Zope] ExternalFile - getting back the file

Hi :-) I'm using the ExternalFile product: http://www.zope.org/Members/arielpartners/ExternalFile because I need to have a file both in ZMI, as well as in filesystem. I would like to ask if anyone can tell me how to get back the file that ExternalFile was created from, having only the object? In fact I do not need the file itself, but tha data (bytes) that were inside. I would be very grateful for any help. Best regards, Maciej Zieba