I Only recently noticed these marks on my cam cover but looking back at old photo's they have been on the car since I bought it

Its not a new thing and they dont leak. Ive known the car since 1992 so I know its nothing sinister. Just wondering if its something other people have seen. They are on both side of where the spark plugs are.

Only thing I can think of is that the car was bought in 1992 with a bust engine. Split block i think the history says. Car had a new block fitted and was taken back down to stage 1.