On Wed, 14 Oct 2020 14:03:20 +0100, "Dave Plowman (News)"
wrote:

snip

Is it a P21W / R335 as that doesn't seem to help or is there a more
common name for them please?


Sounds like a standard car SBC. Although more commonly single contact as
with a indicator bulb. Twin contacts usually twin filament.

They've probably done that to force you to buy spare bulbs from them,
rather than 2 for a quid at Halfords.

Possibly. ;-)

Although cars are now 19w rather
than the older 21w - 24w not common.

No, I'd not seen one before?

Much older cars sometimes did have two contact SBC single filament bulbs.
But LED replacements for them not common, I'd guess.

Ok.

Possible to remove the base from your old bulb and fit a suitable led
cluster to that? Or change the bulb holder?

Well, as I've replied to Paul since, I had a 'what if' along those
lines and assuming the pin spacing / orientation is 'stock'. for
something more common, I could re-wire it so that the base is earth
and then could feed the two filaments as you might with a stop / tail.

So it's just a matter or finding a suitable (LEDS facing straight out
and sideways) LED lamp and giving it a go.

Would you think running stop / rail together would impact the life
span much Dave?

Cheers, T i m

p.s. I'm thinking with a LED lamp, this could be an inspection light
and a general purpose emergency light that could be attached to one of
my several 12V LA batteries. ;-)