So I have dripping shower and some googling tells me I likely need to replace the seats.
When I open things up and have a look, I can't see any notches to lock in the seat removal tool (Raven 4-way). I also noticed that the shower diverter is held in differently than I had seen in YouTube videos.
I put in a new TA-25A diverter spindle and a new TA-10 spindle (had to snap the spindle to get the handle off) and those both seem to be working.
The drip isn't completely gone but it's better.
So are there seats in this thing and how do I get them out?

https://www.askmehelpdesk.com/attachment.php?attachmentid=48444&stc=1

So, after all those views no one has any ideas? Bummer.

By way of closure, I'll tell you what the folks at Symmons think is going on.
(Oh, and before I forget, big thanks to Symmons for their amazingly swift replies to my inquiries.)

Symmons is saying that the seat notches aren't visible because someone stripped them out during an earlier replacement attempt.
And they reiterated the suggestion that I've seen elsewhere about using #6 & #8 easyouts to remove the seats.
They tell me that although this is an older style valve, the TA-4 seats will fit.

Frankly, I'm not inclined to try it because the drip has stopped. If it should return and then go from a drip to a trickle, then I'll reconsider.

Thanks to all who took a look.

Take seat removal tool. It has two ends: skinny one and fat one. Insert the fat on into the seat. Take hammer and tap the end of the seat wrench with reasonable force. Seat wrench end is square with sharp edges. As you tap it, it will cut a groove into the set. Do not move seat wrench, keep it tightly inside. Now lean against the wrench with your body and very slowly start pushing inward and to the left. Seat will start turning.

Seat do not rust, neither does the body of the faucet, meaning it will loose its grip easily.

Let me know how you did

Milo