eBay
Huge ! ! !

This Aero Ektar 6,3/48" has beautyful glass, except some dust inside, and some small dots of changed color in rear coating ( not visible if looking through the lens ). 

Typical  " Tee - color " of rear lens cell is caused by radioactivity.
 You should store it in a remote place and you should not stay closer than 6 feet longer than 60 hours a year. Please
browse the web for information.

 Image circle 510mm.

Heavy ! ! !
200 pounds !