Hey Scott,
Those are seat pans used from about 1960 on until the Mark II's came out when
the perforated became solid sheet steel. The first seat pans on the 6 cylinder
cars were open with no perforated metal like the ones you have. I don't
believe 100-4's ever used a metal seat pan. My BN1 had a wooden seat form
and think the BN2's did also. You might put these in the classified section
as a lot of us have had to purchase them to replace rusty old ones.
Regards,
Mike