I took apart a bank token (Digipass 550 manufactured by Vasco) and this is part of the board, you can see the screw hole with the gold plating together with what looks like a PCB inductor and something that looks similar to a spark gap?

Edit: Device stopped working after removing these screws, called the bank and they mentioned that once taken apart the device auto-destroys

enter image description here

  • \$\begingroup\$ Yeah I would say that is probably what it is, an inductor to block high frequency noise from the casing, and a spark gap to prevent high potential differences. \$\endgroup\$ – Vinzent Jan 10 at 19:04
  • \$\begingroup\$ what kind of a device is that from? \$\endgroup\$ – jsotola Jan 10 at 19:24
  • \$\begingroup\$ @jsotola DigiPass 550 from ING Bank - manufactured by Vasco \$\endgroup\$ – Ned Jan 10 at 19:26
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    \$\begingroup\$ The device seems to be time-aware. Does it receive a European time signal perhaps? \$\endgroup\$ – Spehro Pefhany Jan 10 at 19:52
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    \$\begingroup\$ @Sphero It does have a XTAL running at 32.768kHz and some transistors (seems like Nexperia BC856) that could be used for that. \$\endgroup\$ – Ned Jan 10 at 20:19

The circular trace is an inductor, what it's doing in the circuit is hard to tell, without looking at the other components in the circuit. It looks like it's connected to a ground plane along with the screw. They removed the ground plane around the inductor to avoid capacitance with the ground plane. The thing could be an antenna.

enter image description here

The "spark gap" really depends on if it is there is a gap (which isn't apparent from the picture. It's either for ESD suppression (which might make sense if its attached to a screw. If there is solder mask (darker green hourglass shape) with copper underneath, then it's simply to ground out the fastener .

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