A few corrections to the list:
IDADC
German Automobile Club
There is no special rates for ADAC members anymore since 2006 despite that is popps up in the webpage IHG.
Government rates can be booked but you must shown at the Hotel besides ID also an official document that you are on official business trip. Leisure stays are not allowed anymore..
IMCGV
Canada Government
IMGOV
U.S. Government Rate
Other Membership-based Rates
IVIDS
Travel Agents (Must carry an IATAN Card or Photo ID with a Letter of Authorization on agency letterhead that you are entitled to the discount upon check-in)
Max. 5 nights per stay, max 1 room per travel agent
Airliner max. 7 nights per stay, max 1 room per airliner
IVEDI
Employee Rate (Must present an IHG System Room Benefit Card upon check-in)
onl
can only be booked online.