It could be either an RCBS, Lyman or Lee Ram Prime die. If it doesn't have the part that goes into the shell holder on the ram, or the primer seating rods for both large and small primers, then it's pretty much useless. If it's an RCBS Ram Prime die, look it up on their website, and then call them and ask for the missing parts. You'll have to furnish your own shell holder, but the rest of the parts are available directly from them.
I use both the Lyman and RCBS Ram Prime for almost all my primer seating, and out of all the methods I've tried, it's the best one for me.
Hope this helps.
Fred