Question:

What is the purpose of the MD5 Checksum field in Vault?

Answer:

Vault uses the MD5 Checksum (md5checksum__v) field to identify duplicate content.  This field is available to be used in Reporting but is not available in the Document Properties in the Vault User Interface.  

The label in the Vault User Interface is Checksum for reporting purposes.

Related Documentation:

Vault Field Documentation: Using Duplicate Content Detection