I would suggest that all the holes were punched at once with a double-action press: first action clamps the plate flat in the die, second punches all the holes in one action. The die set for the earlier plate with the notched half-round opening along the top edge would be easier to manufacture than the die set with a forming punch to force the bulged shape in that location.
In any event, punching 1/8th MS plate would need to have the plate clamped to avoid distortion and to ensure the plate strips from the punches as the die set's punches are withdrawn. I also suspect each plate was dipped in a drawing/cutting compound prior to placing into the die.
I suppose the other question is the country of origin: Canadian or Australian manufacture? Both from the same country, or one from each?
Mike
Last edited by Mike Cecil; 12-02-21 at 22:56.
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