I have to agree with Brian. I'm not sure you can justify #50 is simply a rebuild of #1.
In addition to the window arrangement that Brian pointed out, the coach end window arrangement is totally different than the AC&F builder's photo. The Baker Heater is prominent in the builder's photo, yet on #50is in a totally different location in the car, and I'm not sure its a Baker or just a stove. The bolster has a totally different side bearing arrangement.
At the very least, it is a very heavy rebuild since so few of the details match and the window arrangement suggests a different car structure. It clearly isn't just adding steel sheathing.