[Coco] Extended ADOS-3

[Robert Gault]

A disk image of Art's package was uploaded by someone to the Maltedmedia 
ftp site. The file ftp://maltedmedia.com/coco/NEWLY-RECEIVED/ADOS3EXT.DSK
has a corrupted T17S2 sector and none of the contents can be loaded.

Assuming this was released into the public domain (I think Art gave 
permission), is there some procedure to unlock this disk? Is there a 
better disk image somewhere?