'nic whois warning

24.in-addr.arpa has never been delegated.

What do you mean? Address space has been assigned by ARIN:

whois -h whois.arin.net 24.128

Continental Cablevision - North East (NETBLK-CVSN-CCNE) CVSN-CCNE
                                                   24.128.0.0 - 24.128.255.255

There appear to be registered nameservers for some blocks. And just now:

set type=soa
24.in-addr.arpa.

Server: starship.av8.com
Address: 198.3.136.10

IN-ADDR.ARPA
        origin = A.ROOT-SERVERS.NET
        mail addr = hostmaster.INTERNIC.NET
        serial = 1999010400

    --Dean

24.0.0.0/8 is registered to cable-modem providers. Continental Cablevision
Northeast is ne.mediaone.net. Other blocks are registered to @Home as well as
some other providers.

: 24.0.0.0/8 is registered to cable-modem providers. Continental Cablevision
: Northeast is ne.mediaone.net. Other blocks are registered to @Home as well as
: some other providers.

Is it possible to determine when an initial allocation was made for a
given network if said netblock was allocated prior to ARIN?