TIN PACT SPECIAL SESSION THIS WEEK ROUTINE A further special session of the International Tin Council, ITC, held here tomorrow, March 24, will give member countries an update on the latest debate over the hundreds of millions of sterling lost when its buffer stock price support scheme failed in October 1985, delegates said. But the ITC quarterly session scheduled for April 8-9 will be important, as the council will by then be wanting to decide on whether the current pact should be extended beyond June 30 or just allowed to expire, delegates said. A two year extension is possible.