I purchased a few Kennedy 1964 Half Dollars recently and all of them are slightly concave on the eagle side. Is this normal?

Not that I am aware of. Are you sure that they are not counterfeit? Any 1964 half dollars I have ever had have never been as you describe. If you didn't buy online from Ebay or other such place I would suspect you may have been sold replicas. Maybe not but that would be my first impression from what you have described.

Depends on what half dollars you are comparing them to, older half dollars whether silver or not all have a slight concave on the eagle side but newer ones are just flat. Im not quite sure when exactly the US mint started doing this but it seems like they started making 'flatter' half dollars around the 1990's. So anyways, the 'concave' is perfectly normal, no need to worry about it. If you are still concerned with it, post some pictures and I'll make sure for you .

Just compared a '64 Kennedy and a the rest of my halves, didn't seem to notice anything of the sort, could just my coins/eyes, though.

Measure the diameter of the coin. It should match the mint specifications exactly to the millimeter. Fake coins can be slightly larger or smaller due to the unpredictable nature of metal when it is removed from a die and cooled. This can also make a fake coin slightly concave or convex.

Diameter should be : 30.6 mm
Thickness should be : 2.15 mm

Hey Craig, I thought there was a margin of error? Like when measuring yourself, I know the mint was very precise, with their measurements, though.

It's going to be really close to that. The margin comes in when the coins are circulated and wear down but the 64's I've seen aren't even close to the wear factor of older silver coins. If a coin measures more than that, I'd be very skeptical about its authenticity.

Shakuni, can you post a picture?

Hi Sir, I will try to measure it.

There is no point in posting a picture as the concave will not be visible in it as its very slight. It can be felt though if the coin is in hand.

If the concave is very slight it is probably just how the half dollars were made before the 1990s as I mentioned earlier. I'm sure your coins are perfectly fine

Hi Shakuni ,
Can you post your kennedy 1964 photo on here that we can help you check them.