35c
What do I think?
I think you have experienced, something we all have,
the exhilaration of finding a rare stamp.
Nice isn't it

Sadly they generally fail.
Consider perhaps a thousand hands have inspected your stamp
as it arrives in their possession, from that perhaps 500 have checked the watermark.
The chances of finding a rarity, is in itself, a rarity.
But it does happen.
Never give up.