25 Ptas Value ?

I've noticed that the digits in the star are sometimes faint or unreadable even on coins that appear to be otherwise uncirculated.

Which is the condition of the coin, the main detail or the number in the star ?

Pre-euro national currency coins are often sold by weight since plenty is available. This may include coins that were withdrawn from ciruclation in the 1990's. In Spain the latest generations of pesetas were a lot smaller, reflecting decades of inflation.

The coin you've shown is in an exceptional condition, adding to its value. European base metal coins on which you can hardly get a bid over here, are most likely less abundant across the Atlantic. This may cause some price differential.