Bdd1.7z Site

The .7z extension indicates a 7-Zip compressed archive file, which uses the open-source 7-Zip software developed by Igor Pavlov.

If the file is not opening, it may be corrupted during download or transfer. BDD1.7z

Once I have this context, I can give you a more accurate and detailed answer. 7z File Format - Library of Congress BDD1.7z