Moen Model 20B 1st generation, Old shower faucet

[Diddywhat]

Any idea what I have here? Any help identifying it is appreciated. Hot water trickles cold water is just fine. TIA

 

[Marlinman]

This is Moen's 1st generation of valves. They used "Core Assemblies" as opposed to cartridge's.
Parts and assembly

 

[Sponsor]

 

[Terry]

 

[M-DB]

This is Moen's 1st generation of valves. They used "Core Assemblies" as opposed to cartridge's.
Parts and assembly