Can a person sell or use unstamped weights or measures?

No, Weights or Measure shall be sold or offered, exposed or possessed for sale or used or kept for use in any transaction or protection unless it has been verified & stamped that too by a licenced manufacturer/dealer of W & M.

The manufacturer of the weighing and measuring instruments is responsible for getting initial stamping done in r/o the instruments manufactured by him, before they are sold in the market.