50. Allowance for misused stamps

When any person has inadvertently used for an instrument liable to duty a stamp of greater value than was necessary, or has inadvertently used a stamp for an instrument not liable to any duty, the Collector may, on application made within 6 months after the date of the instrument, or, if it is not dated, within 6 months after the execution thereof by the person by whom it was first or alone executed, and upon the instrument, if liable to duty, being stamped with the proper duty, cancel and allow as spoiled the stamp so misused.