Title 14 CFR 45 requires aircraft to have an external data plate. The Stinson has its data plate on the firewall in the cabin. Even though the Stinson is a CAR 3 airplane, it has to comply with CFR 45 for aircraft markings. 

That same regulation allows me to have smaller registration numbers than a new airplane. So the N9391K will be only on the tail. The larger 12″ letters that most airplanes have are not required and the Stinson won’t have them. I think they take away from the beauty of the Stinson. 

External data plate applied.