Thanks,Brian for your comprehensive reply.
I would never have thought that the key could be at least 400 years old.
It has stood the test of time, has a wonderful patina,and is in remarkably good condition.
I think that the Brazing technique has been employed in its construction,the key is 4 1/2 inches in length.
The Trefoil stem still retains its form, the bit is also in good shape,possibly suggesting that it has had minimal usage.
Any idea of it's origin?
Thanks.
Patent.