Diner’s Club? What’s that? Seriously, Diner’s Club has never been a player in credit card circles. It never was accepted very many places. I don’t know its rules; I never had one. Probably the ONLY credit card I’ve never had. I think it was used by traveling saelsmen only. Never widely held.
Strictly speaking it was not a credit card because the balance on the card was due on receipt of the bill.
Visa and American Express did not show up until 1958, Master Card in 1966. So through most of the 50s they had a monopoly and momentum carried them through most of the 60s.