https://en.wikipedia.org/wiki/World_...#Type_approval
Type Approval
The 1958 Agreement operates on the principles of type approval and reciprocal recognition. Any country that accedes to the 1958 Agreement has authority to test and approve any manufacturer's design of a regulated product, regardless of the country in which that component was produced. Each individual design from each individual manufacturer is counted as one individual type'. Once any acceding country grants a type approval, every other acceding country is obliged to honor that type approval and regard that vehicle or item of motor vehicle equipment as legal for import, sale and use. Items type-approved according to a UN Regulation are marked with an E and a number, within a circle. The number indicates which country approved the item, and other surrounding letters and digits indicate the precise version of the regulation met and the type approval number, respectively.
Although all countries' type approvals are legally equivalent, there are real and perceived differences in the rigour with which the regulations and protocols are applied by different national type approval authorities. Some countries have their own national standards for granting type approvals, which may be more stringent than called for by the UN regulations themselves. Within the auto parts industry, a German (E1) type approval, for example, is regarded as a measure of insurance against suspicion of poor quality or an undeserved type approval.
UN Regulations (1958 Agreement)
Regs 41-60 - Transport - UNECE

