The Collaborative International Dictionary of English v.0.48:

Turnplate \Turn"plate`\, n.
   A turntable.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Turntable \Turn"ta`ble\, n.
   A large revolving platform, for turning railroad cars,
   locomotives, etc., in a different direction; -- called also
   turnplate.
   [1913 Webster]