silver dimes

I have always wondered why in my coinstar searches, any silver that i find is mostly dimes? I have found only on silver quarter. Most common find is foreign coins. do they weigh them or electronically test them?

Have been getting skunked with the MD, so decided to get some coins from the bank and try my luck with some indoor coin hunting. I definately got lucky with this box! BTW, I haven't found any silver halves in almost 3 months. Was getting 4-5 per box for the first three months of the year, now...