Author: Alan, 5B4AHJ
The JB prefix has not been used since 1963.
The JB8 prefix was used for a few days in August, 1963, by a DXpedition (JA1BRK/JB8, JA1HQG/JB8, JA1KHG/JB8 and JA1WU/JB8) to Torishima Island (not to be confused with Minami Torishima), and was also used in 1961-62 by JA7QQ/JB, also from Torishima Island (tnx JJ1WTL).
The JC prefix has never been used.
There are many callsigns with JB & JC prefixes in the Club Log QSO database. With the exception of the above JB calls in 1961-1963, these are all busted calls.
The majority of logged JB calls are busted YB calls, with a sprinkling of busted J6 & J8 calls.
Logged JC calls are busted JA, JH, JR, YC and other calls with similar prefixes.
Club Log maps these prefixes as follows:
JB8 - Japan from 1963-08-13 to 1963-08-18
JB - with the exception of the JB8 mapping above, all are mapped to INVALID for all dates
JA7QQ/JB - mapped by exception.
JC - INVALID for all dates.
The following was provided by JARL CIC via RX1AL:
"Prefix 7J is for foreign amateurs who reside in Japan under reciprocal permit since Sept. 17, 1985.Japanese authority has announced on 28 May 1999, that non-Japanese radio amateurs will start to use the same callsign series as the Japanese.It means that 7J prefix will not be issued any more, but existing stations can continue to use their original 7J calls.The 7J block was issued sequentially from 7J#AAA, while 7J6C$$ belongs to Okinawa (normally US military). A club station having a foreigner representative which the authority granted since 1993 uses the 7J#Y$$ block. List of 7J stations in Okinawa: 7J6ADH, 7J6YAB (club station),7J6ADF, 7J6YAA (club station)."
From 2005, the /JI suffix has been used some Japanese Island DXpeditions, eg:
JI3DST/JI3 (11 February 2005), JI3DST/JI1 (July 27-30, 2012 etc.), JF0BPT/JI2 (August 8, 2008), JS6RRR/JI4 (May 20, 2007) etc (info from RX1AL).