Inside the rocker cover of my PI didn't look too dis-similar to that when I got it,
you could just about make out the rockers amongst the sludge.
I do not think the engine was serviced in a very long time, if ever.
Did me about 15k before other things got the engine.
When the block went for cleaning recently, they commented they hadn't had one that bad for a while. I stunk of neglect,