Special double-D style washer for MGA side curtain peg socket mounting. This piece goes below the door top trim rail, underneath the metal door shell top flange. It gives firm support for the side curtain socket to stabilize the side curtain, spreading the load over a large surface area, while covering an elongated slot (that allows some fore/aft adjustment of position of the socket).

PART NO.  SPL.PAGE  DESCRIPTION                                                            
AFH1744   15.R.15   Socket for side curtain peg (2) -(trimming, Tourer, 1500)
AFH1744   16.R.32   Socket -side curtain peg (2) -(trimming, 1600 and 1600-MK-II Tourer)
AFH1744   TC.R.13   Socket -side curtain peg (2) -(door fittings, Tourer, Twin Cam)
AFH2579   15.R.32   Washer (special) for side curtain peg socket (2) -(trimming, 1500
    Tourer)
AFH2579   16.R.32   Washer -side curtain peg socket (special) (2) -(trimming, 1600 and
    1600-MK-II Tourer)
AFH2579   TC.R.13   Washer -side curtain peg socket (special) (2) -(door fittings, Tourer,
    Twin Cam)
FNZ208    15.R.32   Nut for side curtain peg socket (2) -(trimming, 1500 Tourer)
FNZ208    16.R.21   Locknut -stud (2) -(rear bumper, 1600 and 1600-MK-II) Com(C)102381-
    Add distance piece in place of flat washer, and change FNS108 thick nut to thin nut.
FNZ208    16.R.32   Nut -peg socket (2) -(side curtain, timming, 1600 and 1600-MK-II
    Tourer)

Special washer - double-D style:
ID = 0.505-0.520"
OD = 1.00"
AF = 0.733"
Th = 0.120-0.125"