Any certificates should be designed so that forgery and/or alterations are readily detectable. The printing of securities certificates must be entrusted to recognised security printers. The paper for securities must be first class bond or banknote paper containing a watermark of the printer or issuer. If more than one class of securities are listed on the Exchange, the colour of the certificates for each class of securities must be distinctly different. Where an issuer's Articles of Association restrict the percentage of shares held in foreign hands and the shares of the issuer are accordingly designated as foreign shares or local shares, such foreign shares and local shares are considered to be two separate classes of shares for the purpose of this rule.