May be of interest to you: On Delcampe you will find some interesting new postcards of various prototypes, inter-war tanks and vehicles
Delcampe.net -> postcards -> tank
... or type in the following url:
http://www.delcampe.net/items?language=E&searchString=Tank&catLists[]=-2&searchOptionForm[searchMode]=all&searchOptionForm[searchTldCountry]=net&searchOptionForm[searchInDescription]=N
Enjoy!
"Siplicity is the ultimate sophistication" -Leonardo Da Vinci-
