cast resin smoke box doors

[Super]

This is where I have been buying my doors. He has several different sizes. I start by using a caliper on the outside of the face I want to replace and I also measure the inside diameter as the doors also have an inside ridge which, when modified, helps to get the door centered when gluing. I then check all his doors to find one that comes close the these measurements. If you look at my Avatar, that smokebox door on Porter is about the smallest I have done.
http://www.ebay.com/sch/m.html?_odkw=&LH...=&_sacat=0