First of all, there is nothing wrong with using the word "registered" in
1985. SRI-NIC (the original ARPANET/Internet registry) had existed long
before 1985. It originally registered hosts and even their users, but when
domains were invented (RFC 882/883 timeframe, 1983-ish) SRI-NIC was
registering them too.
As for DNS use in 1985, consider that 4.3BSD, the first Berkeley release
with DNS, was released in early 1986, and was definitely working well inside
Berkeley in 1985. So
Berkeley.EDU was up in 1985, and its DNS implementation
incorporated the changes between 882/883 and 1034/1035, i.e., 1034/1035-style
DNS was in operation in 1985 two years before being formally codified in the
RFCs.
In fact I just checked WHOIS and
BERKELEY.EDU was registered on 1985-04-24.
Since it was one of the first, it is in fact quite plausible that there were
indeed 6 domain records in the SRI-NIC registry in 1985.
MS