In the Google map below you will see many color-coded rectangles. If you click on the corner of any rectangle it will ‘select’ and open a balloon with a link to the respective map. The rectangles show the map boundary and the color indicates the date of original publication. You can zoom in and drag the map to get a closer view of the rectangles.
Red = before 1800; Orange = 1800-1849; Yellow = 1850-1899; Blue = 1900-1949; Green = after 1950
These maps are hosted at the Tibet Map Site. You can get more information from there and download individual maps.
Maps of Tibet (157 sheets)