You'd likely want to use the classify service if all you needed was a call number.  It's a different API -- but the one MarcEdit has made use of for the past 2 1/2 years to provide folks with batch call number insertion in either LC or Dewey.  

--tr

-----Original Message-----
From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of Eric Lease Morgan
Sent: Tuesday, July 17, 2012 8:07 AM
To: [log in to unmask]
Subject: Re: [CODE4LIB] worldcat api

> If so, then given an OCLC number is it possible get an LCCN ^h^h^h^ Library of Congress call number, and if so, then how?

Oops! I know I can get an LCCN. Given an OCLC number, what I need is a Library of Congress call number. --Earache