Riddle 22

My last are celebrated, noted, learned:
Some will not come for years, and some are gone--
Ah, never to return. And only one
We may with truthfulness assert, exists.
And yet my first can buy them, eat them too,
And set them if he choose; and upon one
Of them he may perhaps send forth my whole;
Or on it may perhaps inscribe my whole;
Or on my whole he may inscribe my last.