PART NO.  SPL.PAGE  DESCRIPTION                                                           
47330     15.J.4    Key -top end -(adjustable steering column, 1500)
47330     16.J.4    Key -top end -(adjustable steering column, 1600 and 1600-MK-II)-
    changed to AAA193
47330     TC.J.3    Key for tube -(inner top, adjustable column, steering, Twin Cam)-
    optional extra

This square key with rounded ends is called a Feather Key. It is a sliding fit in the keyways of the MGA adjustable steering column, allowing change of shaft length while preventing the upper shaft from slipping all the way out. Part number changed to AAA193 sometime during 1600 model production. The key is 3/16-in square x 1/2-in overall length.

Alternate numbers:
BMC no. AAA193
Moss part number 327-080
McMaster-Carr 90164A231

More information about the assembly in tech article sr107a.htm