Delta's Frequent Flyer Program had Medallion as its only elite level in the late 1980s. (I don't know when they introduced it; it was there when I started serious flying.) It required 25,000 actual flight miles; as I recall: class of service bonuses didn't count, but the segment minimum of 1,000 miles did. Around 1990 or a bit before, they introduced Royal Medallion for 50,000 miles. There were no elite bonus miles. Instead, elites got to choose rewards from a separate schedule with reduced mileage requirements. That was more or less the same, but not exactly, since partner miles (car rentals, etc.) increased in value along with flying miles. This all changed when DL switched to its SkyMiles program in 1995.

One of the best awards on the Medallion schedule was the M2 award: round trip upgrade for 2,500 miles with no fare restrictions. Since you then earned redeemable miles based on where you sat, not what you paid, you could upgrade a trip of over 2,500 miles and earn more additional miles via the class of service bonus than you paid for the upgrade. A win-win, at least for the passenger. Sadly, those days are gone.