Teflon is a remarkable substance. It has the best resistance to chemical attack of any polymer, and it can be used at any temperature between -73 C and 260 C with no effect on its properties. It also has a very low coefficient of friction.
A stale dated warrant is an unredeemed warrant which was issued more than six months prior to the current date. A stale dated warrant is expired and the original instrument is no longer negotiable.
If period is not mentioned, banking practice is six months. There is difference between dividend warrant and cheque. Yes the issuer can. Validity period for a cheque is six months. Dividend warrant and cheque are two quite different things although the concept is that the bank will pay to the bearer money on both occasions.