Here are a couple pics of two shells I have that show some use of the powder can.
The first is one I found that hit a rock and didn't explode but fortunately for me it cracked open showing the construction contents. While you can't see the tin tube going down into the can, much of the power can is intact. It is just as I found it.
The 2nd one is one that exploded but blew out the side. If you look into the shadowed interior you will see in the matrix in the shell bottom a round hole about 1/2 inch deep where the can had been. The rest of the shell has cracks and almost blew apart.
I don't have a half shell of one but I need to get one. I'm sure someone on this forum has a good example they could post a picture of. I understand that in Jack Melton's new half shell book there is a picture on page 272. BTW, while I haven't seen it, I'm sure this book will be a must for all serious artillery collectors. I get mine in Richmond in two weeks. See our sales site in the literature section for info on getting the book.