If you do not already have this, and you are a potter specializing in high temperature glazes, then you should consider adding it to your workshop bookshelf. A wealth of first class information not to be missed.
my shogun is 15 and so worthless - worth less than a koshe Mitsubishi replacement mirror. This option which simply sticks over the broken mirror is a good cheap alternative. It arrived promptly-ish and was easy to fit. I have given it only three stars partly because it took over a week to arrive and partly because it is not a "perfect" fit, merely good enough.