How does the FIA keep track of the teams' power unit allocations?

Question

In 2018, F1 teams are allowed only 3 units of the Internal Combustion Engine, MGU-K and MGU-H, and 2 units of Energy Store, Turbocharger and Control Electronics. Gearboxes must also be used for 6 consecutive race weekends (FP3 to Race) before teams could replace them without penalty.

Question is, how does the FIA keep track of these components and make sure that the teams are not changing them between each race weekend?

Answer 1

Each part of the power unit is affixed with a seal once installed in the car.

These seals are presumably recorded in a system under FIA control. The seals are then checked whenever necessary by the FIA delegates.

A broken seal disallows any further use of a part unless the seal is removed under FIA supervision.

See Article 23.3.d of the FIA Sporting Regulations for detail of the rules for affixing or removing seals.