Blimey!
We've had these style stamps for YEARS!
It doesn't matter when it is used, because when it was purchased it was the going rate for a first class stamp AT THAT TIME.
Inflation makes no difference here because it is still being used to only send a first class letter, and if you paid for the stamp three years ago it means that the Postal Service has been investing your money for three years, so it all evens out in the end.
Simple pimple, really.
Here is a Christmas one......

....(enlarged, of course)
Usually, they are just plain gold, with the Queen's profile in one corner, and "1st" in the other.