My 1911 chassis has, at the rear, castle nuts (holding that little cast bracket on each side), which are with parallel sides, as opposed to castellated nuts which are turned at the castellations to become round where the 3/32" splitpin goes. Is this right? or has someone replaced them at some point? Which were right for 1911?
David

Judging guide shows the 'flat' base castellated as early use, up to 1914. See pic at top.

About 1913 or so, the 'round' base castellated began showing up, but maybe these are right for your car if they seem to have been in place since factory installation?