Hah! I fought the law, but we both won.
The local gendarme decided to question the use of a license plate frame that covers the annual tag; it's current, just not visible. It's also been that way for at least a decade. Officer M. also let me know that one of my four tail light bulbs was out. I thanked him because I truly didn't know as I hadn't driven the car in nearly a month.
I got a warning for both infractions, but I can't help believing this was just another fishing expedition by someone experiencing a slow evening or hoping for some kind of big score; maybe both.
Anyway, I'll keep the license frame but cut it just enough to reveal the sticker. Then I'll check inventory to see if I have the correct bulb or buy a replacement.