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.
The drop dead date in the contract for the buyers to get a mortgage commitment was less than three weeks after signing (hence that provision of the contract has now been violated by the buyers) and I should have been advised by someone that this was a ridiculous date.