Of course, it surely had glass headlamps, so the whole question didn't arise.

Do you remember those huge glass headlamps, quite expensive to replace because of their complexity - didn't some have side lights included?

Wasn't there a Morris car dubbed a "frog-eye"?

Perhaps you are thinking of the bug-eye Austin-Healey Sprite.

I just went out and polished the headlamp which was "foggy". Serve me right, I disregarded the youtube advice about appropriate precautions -  I used a battery rotary mop polisher, just the sponge backing,  and covered my trousers and the car bonnet with Brasso spots! Serves me right.  It cleared up the fog, though.

So I wonder if on those sporty and posh cars where the headlamps retract when the lights are off, as they are on only in the dark, they get no sunlight, and keep their good transparency.
I suppose keeping the car under a car port, or in a garage would help, except that the headlamps would still be exposed when driving during the day.
In fact, if they never dull, I assume there is no need to regularly re-polish them, so the coating doesn't wear off.

Comments please.

There are several YouTube videos advising how to re-polish and restore headlamps, one I watched advising replacing the Anti-UV coat

PS Wasn't there a Morris car dubbed a "frog-eye"?