Yes, but your own text said that the prefix was "usually" omitted.

Gary L. Strawn, Authorities Librarian, etc.
Northwestern University Library, 1970 Campus Drive, Evanston IL 60208-2300
e-mail: [log in to unmask]   voice: 847/491-2788   fax: 847/491-8306
Forsan et haec olim meminisse iuvabit.         BatchCat version: 2007.22.416

From: Program for Cooperative Cataloging [mailto:[log in to unmask]] On Behalf Of Whitacre,Cynthia
Sent: Tuesday, September 11, 2012 8:42 AM
To: [log in to unmask]
Subject: Re: [PCCLIST] Expansion of the OCLC control number

Hello Gary:

Note that the word used in describing the 035 field in the text of this message is "usually" and not "always".