Hi,
These are Offical USGS-DEM (High Detal and Full Color) the Readme says GTOPO30
The folders are like E020N40 the files are labled like:
E020N40.DEM
E020N40.DMW
E020N40.GIF
E020N40.HDR
E020N40.PRJ
E020N40.SCH
E020N40.SRC
E020N40.STX
Extension Contents
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DEM digital elevation model data
HDR header file for DEM
DMW world file
STX statistics file
PRJ projection information file
GIF shaded relief image
SRC source map
SCH header file for source map