Shower stem no nut or packing nut...can't remove need help please!

Any help greatly appreciated!
Trying to remove 2 handle shower stem.........
It has NO "locking nut" or packing nut......nothing to use a long socket on.
The stem itself is in a round threaded brass body which screws directly into the "elbow" of the valve assembly. There is no nut to use those long sockets on. and the threaded body is almost as long as the stem itself.... most the stem is inside the threaded brass body with just enough protruding to attach the handle
There is a thin metal washer just below the top of the stem(atop the threaded brass body) with two very slight flat sides ( wondering if this turns off?)
It turns left to shutoff and right to open?
I was wondering if I just keep turning past open and it will come out but not sure....need help! thank you
the threaded brass body is about 3 1/2 in long , 3/4 in diam, with the stem protruding about a half inch from it.
valve is about 30 yrs old.
was hoping to replace rubber washer on back side of stem as the shower head is dripping/leaking.

Downloading a picture of what you got would surely help us to help you.

Will try to get that for you tomm......Thank you!

It seems to me what you think is the cartridge is really the flange nipple which is around the outside of the actual stem. Use a pliers or small pipe wrench and take off the nipples to access the stems.