It is still not officially opened, but I have been workign on a website dealign with 3/16" scale O Gauge. That was the scale promoted by American Flyer prior to WW2, and adopted by Marx. Here is a link:
http://www.thortrains.net/316scale/index.html
Also, I have a list of measurements in 3/16" scale here:
http://www.thortrains.net/316scale/measures.html
I have a similar list for 1/48 scale . This ought to be of use to people who cannot do fractions:
http://www.thortrains.net/316scale/measures48.html
Happy railroading!