Use and custody of Form D certificates: government officers complete and retain counterfoils; dealers file originals and allow inspection. Form 'D' certificates must be completed and signed by the authorised government officer, who retains the counterfoil and gives original and duplicate to the selling dealer; the counterfoil is to be maintained for a specified period. Dealers claiming sales to the government must furnish the original portion to the Commissioner within the prescribed filing period with the statutory statement and produce the duplicate for inspection if required; the assessing authority may require production of the duplicate.