Thanks for the file. It obviously helped, but I am not sure how. I probably should have taken careful notes about what I did by way of disabling and removing the .ttf fonts and then dragging in the .dfont variety. At one stage when I brought up a Hoefler document in Word, the regular Hoefler text had disappeared. I panicked and removed the .dfont version. Later, after trying something else, the text came back but (judging by the numerals) it was not Hoefler. To make a long story short, all styles of Hoefler (including italic and black) are now working. There are no duplicate font files—I used Remove Duplicates—but I have no Hoefler file in either of the two Fonts folders, even though I can see Hoefler Text in Font Book! To be safe, I used Font Book to export the Hoefler Text to a back-up folder, and the version it exported is the .ttf version. In Get Info I confirmed that it’s the 6.1d7e1 variety. I restarted the computer twice, and determined that this situation is stable. Go figure.
In any event, you set me on the right road. Hoefler Text is now working as it should. I appreciate your help.