A question on key name conventions

[kishnevi]

A simple thing.

Years ago, I was taught that when writing the names of the keys out, major keys are capitalized, and minor keys are not.

Thus

B Flat Major  and d minor

But nowadays everything seems to be capitalized, and if major and minor are differentiated, it's by the simple usage of dropping "major"  and writing out the full key name only for minor keys

Thus

A   for what I learned to write as A Major
A minor (or Minor) for what I learned to write as a minor.

So my question:

Is the convention I learned something that's been abandoned?  Or simply something that was never really a convention in the first place?

[Opus106]

Here's what I've gleaned: drop the M-words.

What is called "A major" is 'A', while "A minor" is simply 'a'. When you get a chance, look at Gurn's signature while he's listening to a Haydn trio in 'eb'.