ESRB certificates for Metal Slug X and Front Mission 3 indicate both titles will be released as PSOne Classics sometime soon.
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Both titles got ratings of T-for-Teen, for violence. Examiner, which spied the listings first, notes that Front Mission 3 was re-released on the Japanese and European PlayStation Stores in March 2009 and September of this year, respectively.
Metal Slug X, a 2001 game for the PSOne, features more content and improved graphics over Metal Slug 2.
Front Mission 3 and Metal Slug X coming to U.S. Playstation Store [Examiner.com]