It looks like 8 of 21 to me as well. #1,4,7,13,15,17,20 & 21
Picture is bad but I see 7 silvers clearly with the 8th being tarnished, but the ones that look like regular clads could be well worn casino halves, so they all could very well be 40%'s but it's really hard to tell from your pic.
My guess is that you woulden't be asking if they werent all keepers. The ears would pick up on the silver if you drop them from one hand to the other. If your still not sure, you could always look at the dates.... lol
Mojo