Two versions of the Boxford power-feed apron were made: the first type, an exact copy of that fitted to the American South Bend lathe, was fitted with a metal screw-in knob to engage the drive. The second type was similar but of more complex construction, this being produced as a safety improvement - its black plastic engagement knob, unlike the metal type, remaining stationary as the drive worked.
The early apron (with data about dismantling and rebuilding this unit found here) and the second type, with pictures of a dismantled unit and the various parts, shown below.