Not really a sign as you can't see it from the road. My guess is it was just a unique piece of equipment so they kept it in good shape.
If anyone knows what this tankcar was used for, please let me know. There is a GATX plant close to me (Sharon PA) I have found these online: http://www.signone.com/images/banner-gatx.jpg http://img.clubphoto.com/jerboa/98361128/hi/null/image.jpg
I doubt it was used for much more than a display. I don't see any obvious brake rigging, air reservoir, etc. Boxcab E50