These are two Hero Brain Implants from The Manchurian Candidate. These things are TINY (as shown by the picture, that's an actual dime...). They both open up to reveal a little piece of brass-colored metal which was never seen on screen, but I believe there may have been a scene shot where they show them being opened and examined...

Here's a shot of them opened revealing the little brass
colored metal plates inside:

And some screen shots:
First two show Ben (Denzel Washington) spitting one out after
having bitten it out of someone:

And this is a shot of a computer monitor showing an 'x-ray' of the device
(Obviously just a graphic created for the film, but still kind of cool...)