Any 90% coin is going to shine and almost glow when mixed with clad in a roll. The 40% halves are usually very easy to spot edge checking as well. These coins from what I understand are 90% silver bonded over a copper core which averages out the weight to about 40% silver overall.
You will find 40% coins that are worn have copper type edges essentially cause silver has been lost through the years and likely due to some use in a slot machine back in the day. Occasionally the face or reverse may also be worn to the point where moisture will rust that part...I will try to get you some pictures if possible.
Overall from my experience with half dollars, it doesn't make a whole lotta sense to date check... The silvers you find this way are few and far between and likely not worth melt. I advise you date check a couple grand to see how long it takes you in comparison too edge checking and decide if it's worth it at that point.
Some might chime in that a dirty edge can trick you but after awhile you get to a point where you know the difference between a dirty silver and a typical clad - when in doubt, check!
Please let me know if I can clarify anything and good luck with whichever method you choose!