Romeo's mother was precisely what I had painted her — a Lady Montague of the severest, with coffee-coloured point-lace, a Cornelia one shade too stout for the mother of the Gracchi.

I am inclined to hold that if there is a plurality of objects that fall under the designatum of a term, then that should be sufficient (though not necessary) to conclude that that is a general term, even when it has a singular occurrence in a sentence.

They may be a rock band, but their retro style shows a heavy Motown influence.

The majestic proportions of this bridge may be partly realized by a few comparisons. […] This bridge would overspan the Capitol at Washington and clear the top of the dome by 51 feet.