Brian the stem and the aperture are all one piece. Unless youv'e got a 2A SA which means the aperture is threaded into the stem. A 1A SA will just have a flip down aperture inside of it, I believe there is a very small pin holding this type in.
To remove the stem you just have to turn it up as far as it will go and then pull it off.
I think 99Trix has a few pics of a Lyman in the "Misc" thread above this at the top of the page.
Last edited by mad_dog; 12/08/11.
