Need Cartridge for shower but no model number 1978

[CoastieGirl]

My Shower has a slow leak coming from the handles and sometimes Shower head. Depends on how you have the spray shower headset. It's a small drip but I need to replace both cartridges I believe these are original to the house 1978. Can you tell me the brand or what cartridge I might need. I am trying to do myself. I have the metal octagon tool to help me in this effort.

 

[Breplum]

Remove the cartridge, measure length and send pics. Most times one needs to own a deep socket set (they make a set for old valves like this).