What do I need for Shower Cartridge? (Pics)

[Helpimdrowning]

I had a leaky shower diverted that I replaced and fixed but (what I believe to be) the shower cartridge also has a small leak but I can not determine what part it is because it has no markings on it. I thought it was a Delta 1600 series cartridge but the more I look at it I don’t think it is. Also any advice on how to remove it would be much appreciated.

 

[Breplum]

Delta OEM#RP1991
ck out http://barrywalter.com/uploads/1/0/5/7/105704383/single_lever_cartridges_10-21-22.pdf