Bottom Arm pivot pin

[WNX700H]

Have been stripping the suspension on my car and have noticed a difference between the left and right hand side lower arm pivot pin. Where the large diameter end of the pin sits in the subframe , one of the pivot pins has a flange on it larger than the diameter on the subframe so the pin will pass through the hole in the subframe until the larger diameter stops it going any further. All the other pivot pins I have seen have not had this flange on them. Was this an earlier design or a modified part for competition as the car I have has various works parts on it?

[ivor badger]

Early ones had no flange. it was std production that the flange was fitted, sometime in the mid/late 60s