I can't seem to find this shower stem. I know it is not Price Phister.
Does it look familiar to you? (see attachment)

Your best bet is to take this to a large plumbing supply outfit. Their guys always seem to recognize stuff for me. That or Tom will be here shortly

Rock, What was the brand name of the mixing valve the stem came out of? Back to you, Tom

It is definitely not Price Pfister stem. Is hard to tell you brand name by just looking at the stem. Only few maufacturers have distinctive stem designs. All others are pretty close with minimal changes...

Can you post a photo of the faucet? Or brand name?

Rock, What was the brand name of the mixing valve the stem came outta? Back to you, Tom

I don't know. It was in when we bought the house, and there is no access behind the tile.

Look closely at all components of faucet that you can see. Handles, etc, there may be a name brand that is very hard to see. Now, why do you want to replace the whole stem? What is the problem with it? May be able to just repair without replacing complete stem. Let us know what your thinking.