The Producers Guild of America is making headway in getting its “Producers’ Mark” into film credits as David O. Russell’s “Silver Linings Playbook” is the latest 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 — will also be used for the indie comedy-drama “Lonely Boy” and is in the credits of Mira Nair’s “The Reluctant Fundamentalist,” which opened the Venice Film Festival. Other pics to feature the mark include the Prohibition era drama “Lawless” and Rob Reiner’s drama “The Magic of Belle Isle.” 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 mark has been given to “Silver Linings” producers Donna Gigliotti, Bruce Cohen and Jonathan Gordon. The comedy, which opens Nov. 21, is produced by the Weinstein Co. and Mirage Enterprises with TWC distributing. Pic stars Bradley Cooper, Robert De Niro and Jennifer Lawrence. Certified producers on “Lonely Boy” are Troy Daniel Smith and Alev Aydin for Exit 43 Prods. The film, a comedy about a schizophrenic bachelor played by Aydin, is currently in post-production. 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.