Letters loved by angels

• Sign of a smash: Abbr
• Maximally crowded into a class
• Box office ltrs
• Hit show's sign
• B.O. advisory
• Sellout sign letters
• Good sign for producers
• Sold-out sign
• Capacity descriptor, briefly

Wikipedia Word definitions in Wikipedia
SRO may refer to: Standing-room only , an event in which all seats are occupied leaving only places to stand Standing Room Only (disambiguation) S.R.O. (album) , a 1966 album by Herb Alpert and the Tijuana Brass S.R.O. (radio program) , a Philippine radio ...