$ openssl crl -in test/revoke.crl -inform der -noout -text -crlnumber | head
crlNumber=1249
Certificate Revocation List (CRL):
        Version 2 (0x1)
    Signature Algorithm: sha512WithRSAEncryption
        Issuer: /C=AU/ST=New South Wales/O=CAcert Testserver/OU=http://cacert1.it-sls.de/CN=CAcert Testserver Root
        Last Update: Jun  6 00:04:27 2018 GMT
        Next Update: Jun 13 00:04:27 2018 GMT
        CRL extensions:
            X509v3 CRL Number: 
                4681


$ openssl crl -in test/class3-revoke.crl -inform der -noout -text -crlnumber | head
crlNumber=010008
Certificate Revocation List (CRL):
        Version 2 (0x1)
    Signature Algorithm: sha512WithRSAEncryption
        Issuer: /O=CAcert Testsever/OU=http://cacert1.it-sls.de/CN=CAcert Testserver Class 3
        Last Update: Jun  6 00:04:29 2018 GMT
        Next Update: Jun 13 00:04:29 2018 GMT
        CRL extensions:
            X509v3 CRL Number: 
                65544