4 reales: Assayer ? [решено]

Hi!
I have this Spanish coin that, due to the weight (13.7g) and the diameter (28.1 mm) I have catalogued as 4 reales.

Now, the questions are two. One is about the assayer. Would you say that the one under the P looks like a R or a B?


Second, would you agree that this castle seems double struck?


Thanks for your help!
B.

It's 4 reales of Potosí of Felipe IV before the https://en.wikipedia.org/wiki/Great_Potosi_Mint_Fraud_of_1649

The mark of the assayer is, I think, overlapping T and R, belonged to Pedro Treviño 1638-1645.

In the shield the eagle of Tirol is doubled, in place of the lion of Flanders.

Thank you for your enlightening reply, Zegeri!

A question: where can I find some references about this coinage? I have a couple of books (Numismatica Espanola from Calico, Calico, Trigo and The Practical book of cobs from Sedwick and Sedwick) but..the more the merrier

B.

In Standard Catalog is in Bolivia KM#17a

I see! Thanks!