The other day I found that the University of North Dakota, Grand Forks, ND, USA holds a series of papers (microfisched) relating to mostly early American armour (although forien vehicles are on the list too). Combat use and development of tanks including some unit war diaries like War Diaries for 345th (327th) Battalion, Tank Corps August to December 1918 and War Diaries for 304th (1st) Brigade, Tank Corps October 1918 to February 1919, various reports, tests, photographs etc.

Their holdings are listed at:

http://webapp.und.edu/dept/library/Collections/og1360.html and include items such as:

If that link doesn't work click here

The archivist librarian for their special collections is contactable at und.archives@library.und.edu

Copying fees and information http://webapp.und.edu/dept/library/Collections/contact.php 

Hopefully this will help someone with their research.