Possible Clues:

• Class novelist has all the keys
• Race bookmaker is capable of handling all types from a particular carriage
• Device, kind used by hack?
• 'Puts the keys of the future at your fingertips' (Philadelphia, 1876)
• Longest word obtainable using only the top line of a normal keyboard
• Style followed by novelist that creates many characters
• Device with which to categorize author?
• Wire pretty complex printing machine
• With 49-Across, where 17-, 24- and 39-Across are seen
• Former secretarial tool