Look for 1987 halves and 1970, those dates were not made for circulation and are hard to find. Also anything 2002 and later was not made for circulation and is harder to find too, though not as rare as the 1970.
Finally got the 1987d I needed last week. Only keeper in the box, but better than nothing. I also found a 1920 British penny in bad shape, but very cool to find

1970 Half dollars are also 40% silver from sets only!
1964 and before are 90% silver and currently are worth $12.50
Half dollars 1965-1970 are 40% silver and are currently worth $5.10
