1983 240D head gasket, cylinder block black build-up

[elemental]

Hello.

I am looking (to buy) at a 1983 240D with an odometer reading of 87000 mil. The engine looks mostly clean but I have noticed a bunch of greasy black build-up near the cylinder closest to the firewall right below the exhaust manifold pipe for that cylinder. All other area of the cylinder block looks clean.

Can someone explain to me what this buildup is caused by? and if it a reason for concern, is it possible that the cylinder head screws came loose?

Any and all comments will be appreciated.