I'm currently looking for a Monaco Gulf, e.g. the CW211 or CW213 (or similar, there seems to have been so many !!) I notice some list the crystal as being acrylic, and some say sapphire. Now, I have a WK1212 as a daily, and it is bombproof, so am a fan of the sapphire crystal - and I'm wondering if the acrylic crystals are 'fragile', or, should it ever need replacing, can you fit a sapphire crystal to and 'acrylic' model - an upgrade, if you were.