Sonny Capone, the only child of the infamous prohibition-era gangster Al Capone, had reportedly been living in the Auburn area in relative obscurity. His daughters are now selling his estate, including Al Capone’s Colt pistol that Al dubbed “sweetheart,” his diamond-monogrammed watch, diamond-studded jewelry, bedroom furniture from his Palm Island home, family photos, a home movie of Capone and his associates, a prison letter to Sonny, according to a statement Monday from Witherell’s Luxury Asset Auctioneers and Appraisers.