You should see a 4 digit code on sidewall for manufacture date...example 3909 would be the 39th week of 2009.
Any true road touring tyre is going to struggle with loose gravel and sand on bitumen roads, your riding awareness is the key. Michelin Road 6 are getting good reviews on the ST1300, but not available in GT spec, maybe the ST1100 is different? Pirelli Angel GT (A Spec) is another good performer on ST1300, may be an option? Remember, different riders get a different feel. Enjoy!