This was linked on HackerNews as well, and one of the comments there is almost as insane as this Bloomberg story:

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I have worked in card payment industry. We would be getting products from China with added boards to beam credit card information. This wasn't state-sponsored attack. Devices were modified while on production line (most likely by bribed employees) as once they were closed they would have anti-tampering mechanism activated so that later it would not be possible to open the device without setting the tamper flag.

Once this was noticed we started weighing the terminals because we could not open the devices (once opened they become useless).

They have learned of this so they started scraping non-essential plastic from inside the device to offset the weight of the added board.

We have ended up measuring angular momentum on a special fixture. There are very expensive laboratory tables to measure angular momentum. I have created a fixture where the device could be placed in two separate positions. The theory is that if the weight and all possible angular momentums match then the devices have to be identical. We could not measure all possible angular momentums but it was possible to measure one or two that would not be known to the attacker.

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