Instrument bulbs : 12v or 14v?

[geeman237]

I’ve noticed when buying various car bulbs, instrument and warning bulbs for older cars, that my local parts store has bulbs for 12 and 14v.
Why do they have two types? Aren’t all cars 12v?
Specifically I was looking for the capless warning bulbs on a Triumph TR6.
FWIW I’m in the US.

[Dave.]

Most alternators pump out around 14v.

[Coilspring]

Sure it wasn't a choice between 12v or 24v ?

I know alternators charge at around 14v but bulbs here (in uk) are rated at 12v or 24v. 14v are not listed, at least not generally .