These are standard '68 Riviera full chrome hubcaps on 15" painted steel rims. The 15" hubcaps were the same for all full size '68 models, with different plastic inserts - Tri-shield emblem for LeSabre, Cat emblem for Wildcats, and an 'R' emblem for the Riviera. :TU:
I have a set of four from an Electra, which look very close to those. As Phil says, the centers are different.
I have a nice set of what I think is the same cap. They were off of a one owner 68 riv. If you need pics let me know and I will grab one.
The 1967-68 Electra wheelcovers were different, they were concave, they covered the entire rim and their centers were made of pot metal. They had a galvanized steel ring at the back like the wire wheelcovers and the Super Deluxe wheelcovers on Rivs. The standard Riviera wheelcovers were much lighter, they didn't cover completly the rims, their center section was made of plastic and they lacked the galvanized steel ring of the Electra covers. They also had a different shape. There is an old Ford pick up that has been used for years as a snow plow in a local servce station with '68 riv wheelcovers on it. The plastic centers were removed in the front ones to leave space for the hub locks.
Ah, right you are.:TU: I just had second, closer look at the pic above, and discovered the difference. Are they worth keeping?? They have a few dings from being tapped onto the rims, nothing major though.