Belgium Precancels

Precancels (in Belgium called "voorafstempelingen" or "pré-oblitérés" ar normal stamps that have been used, and are still being used for the mailing of bulk mail. They are cancelled on sheet by the Belgium Post Office to reduce the workload on handling the mass mail.They will not be canceled by normal cancel devices. They are allowed to be used when submitting at least 1.000 pieces and since1970 at least 500 stuks at the same postoffice.