Automotive lighting is a heavily regulated sector. Virtually everything that functions on the outside must bear the E label. This round symbol with a capital “E” and a small number is the approval mark of the ECE.
Car fans and parts suppliers occasionally complain to me about being led around by the nose by bureaucrats in Brussels, seat of the European Union. But they are being doubly unfair, because the ECE has very little to do with the EU. The ECE is a UN organization and older than the EU. The Economic Commission for Europe (ECE) is headquartered in Geneva, outside the European Union.