The magnification, on the right, shows clearly that the letter is an R not a P. But, because the diagonal of the R coincides with a groove in the milling, the indentation is weak and badly-defined.
It is indistinct, especially to the naked eye, but it is definitely there, indicating that these ‘Pemember’ coins are minor imperfections rather than errors. Of course, it cannot be said from this that all supposed ‘pemember’ coins are mis-hits and that there are absolutely none where a die for a letter ‘P’ has been used in place of an ‘R’, but just keep this in mind:
So, what is it worth? Well, the value – financially – of anything is measured by what someone is prepared to pay for it. Stories in the press initially said that the coins were changing hands for ‘under £10’. Within a matter of days this had risen to as much as £40 but it quickly settled to less than half of this.
The value will probably drop much further when it is realized that this is not a mint error, just a very minor fault, and when everyone who wants one, already has one (or more).
It is the scarcity which puts up the value and these coins are not really rare.