The Producers Guild of America has made more headway in getting its “Producers’ Mark” into film credits as DreamWorks Animation’s “Rise of the Guardians” becomes the sixth pic to commit to carrying the certification.The mark — a lowercase “p.g.a.” that designates individuals certified by the guild as having performed producing duties — was first seen at Cannes in May when it appeared on the Prohibition Era drama “Lawless.” It’s also in the credits of Mira Nair’s “The Reluctant Fundamentalist,” which opened the Venice Film Festival, David O’Russell’s “Silver Linings Playbook,” Rob Reiner’s dramedy “The Magic of Belle Isle” and indie comedy-drama “Lonely Boy.” The certified producers on “Rise of the Guardians,” distributed by Paramount with a Nov. 21 release, are Christina Steinberg and Nancy Bernstein. The Producers’ Mark is given only to producers who request it and who have been certified through the PGA arbitration process. Companies remain free to recognize other individuals with the traditional “produced by” credit as they deem appropriate. The PGA, which has more than 5,000 members, first unveiled the “Producers Mark” concept in October 2010. More than 150 notable producers — including Lorenzo di Bonaventura, Clint Eastwood, David Heyman, Jeffrey Katzenberg, Graham King, Neal Moritz, Scott Rudin and Steven Spielberg — publicly endorsed the idea as a way of bolstering the guild’s decade-long campaign to combat the proliferation of producer credits in film and TV. People familiar with the current situation said the PGA has signed but not yet announced at least two other studios besides TWC, Magnolia and DWA. The companies will provide a “Notice of Producing Credits” to the PGA, just as they currently do for awards contenders, but now no later than the commencement of post-production.