well If you go to Royal I have had the tellers ask me if I wanted to order the Half dollars. I never did so not sure what you would get. But as stated above you will NOT get any silver. they are all pulled out. As for the "silver" dollars no you cant order them in. You will just have to get lucky when ppl bring them in.
10xloupe I'm dont think he meant actual silver dollars. thats just the nick name for the older dollars including the nickel ones. I ask for silver dollars every time I go in, and if they do have any they give me the nickel ones. Its just based off there color not content. :P