During MGA 1600 production the BMC part number changed from AFH2587 to 53K126. This was likely done to consolidate different part numbers from various prior car companies to the newer BMC standard fasteners part number (after the BMC merger). It leaves open the question if the design may or may not have changed at the same time.

PART NO.  SPL.PAGE  DESCRIPTION                                                            
AFH2587   15.R.1    Screw fixing panel -(14 for front valance, body shall, Tourer, 1500)
AFH2587   15.R.1    Screw fixing bracket -(2 for bonnet lock safety catch, body, Tourer)
AFH2587   15.R.3    Screw fixing front wing to sill (6) -(body shell Tourer, 1500)
AFH2587   15.R.3    Screw fixing rear wing to sill (4 at front of rear wing) (body 1500
    Tourer)
AFH2587   15.R.4    Screw fixing splasher to front wing (2 at bottom) (body Tourer, 1500)
AFH2587   15.R.5    Set screw for fascia panel fixing (3)
AFH2587   15.R.5    Screw fixing panel (14) -(valance panel, body shell, 1500 Coupe)
AFH2587   15.R.5    Screw fixing bracket (2) -(bonnet lock safety catch, body shell, 1500
    Coupe)
AFH2587   15.R.7    Screw fixing front wing to sill (6) -(body shell 1500 Coupe)
AFH2587   15.R.7    Screw fixing rear wing to sill (4 at front of rear wing) (body 1500
    Coupe)
AFH2587   15.R.10   Screw fixing boot lid hinges -(12) -(boot lid, Tourer, 1500)
AFH2587   15.R.17   Set screw for bonnet hinges (12) -(bonnet lid fit's)
AFH2587   15.R.40   Screw fixing demister nozzle (4) -(to bracket, sundries, 1500)
AFH2587   16.R.1    Screw fixing panel (14) -(body shell, 1600 and 1600-MK-II Tourer)-
    changed to 53K126
AFH2587   16.R.1    Screw fixing bracket (2) -(bonnet lock safety catch, body shell, 1600
    and 1600-MK-II Tourer) -changed to 53K126
AFH2587   16.R.3    Screw fixing front wing to sill (6) -(body shell 1600 and 1600-MK-II
    Tourer) -changed to 53K126
AFH2587   16.R.3    Screw fixing splash plate (2) -(front, body shell 1600 and 1600-MK-II
    Tourer) -changed to 53K126
AFH2587   16.R.3    Screw -rear wing to sill (4) -(body shell 1600 and 1600-MK-II Tourer)
AFH2587   16.R.5    Screw -fixing panel (14) -(front valance, body shell 1600 and
    1600-MK-II Coupe)
AFH2587   16.R.5    Screw -fixing bracket (2) -(bonnet lock safety catch, body shell 1600
    and 1600-MK-II Coupe)
AFH2587   16.R.7    Screw -front wing to sill (6) -(body shell, 1600 and 1600-MK-II Coupe)
    -changed to 53K126
AFH2587   16.R.7    Screw fixing splash plate (2) -(font wing, body shell, 1600 and
    1600-MK-II Coupe) -changed to 53K126
AFH2587   16.R.7    Screw rear wing to sill (4) -(body shell, 1600 and 1600-MK-II Coupe)-
    changed to 53K126
AFH2587   16.R.10    Screw fixing hinge (12) -(boot lid fittings, 1600 and 1600-MK-II)-
    changed to 53K126
AFH2587   16.R.10    Screw fixing bracket (3) -(striking plate, boot lid fittings, 1600
    and 1600-MK-II) -changed to 53K126
AFH2587   16.R.18    Screw fixing hinge (12) -(bonnet fittings, 1600 and 1600-MK-II)-
    changed to 53K126
AFH2587   16.R.18    Screw support angle (8) -(fascia panel, 1600 and 1600-MK-II)-
    changed to 53K126
AFH2587   16.R.43   Screw fixing nozzle (4) -(sundries, 1600 and 1600-MK-II) -changed to
    53K126
AFH2587   TC.R.1    Screw fixing panel (14) -(front valance, body shell, Tourer, Twin Cam)
AFH2587   TC.R.1    Screw fixing bracket (2) -(bonnet latch safety catch, body shell,
    Tourer, Twin Cam)
AFH2587   TC.R.2    Screw -splash plate to wing (2) -(front, body shell, Tourer, Twin Cam)
AFH2587   TC.R.4    Screw fixing panel (14) -(front valance, body shell, Coupe, Twin Cam)
AFH2587   TC.R.3    Screw -rear wing to sill (4) -(body shell, Tourer, Twin Cam)
AFH2587   TC.R.4    Screw -fixing bracket (2) -(bonnet lock safety catch, body shell,
    Coupe, Twin Cam)
AFH2587   TC.R.4    Screw -front wing to sill (6) -(body shell, Coupe, Twin Cam)
AFH2587   TC.R.5    Screw -splash plate to wing (2) -(front, body shell, Coupe, Twin Cam)
AFH2587   TC.R.6    Screw -rear wing to sill (4) -(body shell, Coupe, Twin Cam)
AFH2587   TS.R.9    Screw -fixing hinge (12) -(boot, Twin Cam)
AFH2587   TS.R.9    Screw -striking plate (3) -(boot, Twin Cam)
AFH2587   TC.R.17   Screw -fixing hinge (12) -(bonnet fittings, Twin Cam)
AFH2587   TC.R.52   Screw -fascia panel to body (3) -(fascia panel, Twin Cam)
AFH2587   TC.R.54   Screw -fixing nozzle (4) -(demist, sundries, Twin Cam)

Original screws with pointed tip AFH2587 changed to 53K126

Replacement screw from Moss UK 53K126 Moss USA 466-385

Fastener kit from Moss USA 321-948 (for front valance panel)

Pointed tip on this screw is very important for production at the factory, as most of these screws went onto floating cage nuts where the pointed screw tip would catch and center the floating nut before engagement of the threads. I (Barney) believe that all screws before and after the change of part number had the pointed tip all through production. Where in the Service Parts Lists it states "AFH2587 not available; use 53K126", what they intend is to deplete inventory under the original part number before moving on to use the new part number. In cases where they intend to immediately abandon the old part and always use the new one (like higher pressure radiator cap), it would say, "always supply xxXxxx" (the new part number). Original screws would be Unified thread standard (fine thread UNF), and should have a round dimple in center of the screw head.

The flat tip part would be the modern aftermarket offering for a replacement part (not as original). American SAE threads are very close and are interchangeable, but would not have the round dimple that signifies (Unified thread). There has been a lot of public discussion on this issue where some people think the flat tip may have been a cost reduction move before end of production. Not yet resolved as of this writing in late 2021; still looking for examples of known unmolested late production MGA to see if any of those cars may have left the factory with flat tip screws (and the dimpled head for unified threads).