ECPrivateKey ::= SEQUENCE {
   version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
   privateKey OCTET STRING,
   parameters [0] ECDomainParameters {{ SECGCurveNames }} OPTIONAL,
   publicKey [1] BIT STRING OPTIONAL
}

We now do not care about the order of [0] and [1], allow multiple copies of them, and allow extra data.