Complex sentence: Stuart Holbrook, the president of Thierault's (a leading auction firm dealing with dolls and childhood ephemera), estimates there are only 20 A. Marque dolls in existence, and refers to them as the "Holy Grail of collectible dolls".
Split into simpler sentences: Stuart Holbrook, the president of Thierault's (a leading auction firm dealing with dolls and childhood ephemera), estimates there are only 20 A. Marque dolls in existence. Holbrook refers to them as the "Holy Grail of collectible dolls".