Actually, 25 dollar for this coin is a good price. The coin is 'ein unze Feinsilber', which translates to one ounce of fine silver (.999)
The Philharmoniker is one of the better known bullion series, in this case from Austria. The series is especially known for the more excessive coins, like the 'Big Phil', a 1000 OZ gold coin made in 2004 with a face value of 100.000 Euro.
Milk spots are indeed white spots which appear over time at the surface of bullion coins. There's not much you can do with it. Canadian Maple Leafs are notorious for getting milk spots.
If you like toned coins, don't mind bullion rounds with a bit of a premium and if you're not just into hording
ASE's, then this one is definitely a good coin at a good price, I'd say.