Get all attachments via API is not visible

Attachments added via the API and the SAP idiosyncratic interface to a to a supplier invoice are lone disposable 1 by 1 with this parameter:

/API_CV_ATTACHMENT_SRV/GetAllOriginals?BusinessObjectTypeName='BKPF'&LinkedSAPObjectKey='123 10000000272024'

How tin I retrieve the database of each attachments? When I effort this via Postman:

API_CV_ATTACHMENT_SRV/GetSAPObjectDocumentType?SAPObjectType='BKPF'

It returns bare due to the fact that "SAPObjectType": "" for the uploaded attachments.