Reynolds

Yes, I think this should be a reserve decal on the left petcock. But the gold border, black background, gold text decal appears to me to a line of small text rather than the simple word "RESERVE".
We need a period photo of this decal on any bike, Norton/Matchless, to see what it must be.

here is another unclear photo of an unrestored P11 tank, again not clarifying the decal words or letters.
A 2014 eBay sale.

Might say "This side reserve"

Aint neva seed a deekle like et.

This is an old thread that kind of morphed in a good way. It thas expanded to the various types of decals on the Hybrid P11/P11a/Ranger. I am thinking starting a new thread, (Or someone else can start it) dedicated to the different transfers used, so as not to derail the OP. I have learned a thing or two from just the wealth of knowledge. I'll dig up some pics for the oil tank and Teledraulic spring fork decals for the front fork yokes. I would like to know if there was a Made in England transfer used on the fender.
Cheers,
Thomas