GB.com has been sold according to whois records and is now displaying domain name brokerage firm Guta.com.
I contacted George Hong, CEO & Founder of Guta.com, who was able to confirm that Guta brokered the domain name sale but the details of the deal have to remain confidential.
GB.com was owned and used by CentralNic for many years and offered sub-domain names on the domain name. Some of which are still indexed today:
CentralNic announced in May 2016 that it was sunsetting the sub-domains on GB.com, on April 30, 2017. This clearly upset the many people who had built websites on the sub-domains. Some domain registrars that offered the sub-domains, stated that the domain was an alternative for Great Britain at the time.
I would expect the sale of GB.com to be US seven figures at a minimum.