(b)if he is of opinion that such instrument is chargeable with duty and is not duly stamped, he shall require the payment of the proper duty or the amount required to make up the same, together with a penalty of the five rupees, or, if he thinks fit, [an amount not exceeding] [Inserted by Act 15 of 1904, Section 6.] ten times the amount of the proper duty or of the deficient portion thereof, whether such amount exceeds or falls short of five rupees: