Not a Briggs engine at all.
It's a cheap £9.00 Chinese engine using the horrible TORCH manufactured spark plugs.
You maye able to find a cross reference for it on the net and then obtain a proper brand of plug to replace it with from your local garden machinery agent- either that or ring them first with the plug number and they may be able to cross reference it for you.
As for a spanner any tool supplier can supply.
pleasant, April 2009