I recently acquired a Mul-t-Lock C series 1/'2 inch shackle padlock. It's very large and well designed. I also noticed a Master Lock No. 3 padlock actually fits inside this locks shackle.
Here's a couple pictures of these new friends hanging out together.
I have taken this lock apart, and I'm impressed with it's construction. I'm hoping to put together a PDF with full tear down photos in the near future.