I used to work for kent cams (1982-3)
My first job there was straightening , cleaning & Parkerisation of the cams (phosphating)
I had to polish & tape the bearings on the a series cams , before phosphating
so they were polished metal to the bearing surfaces , but lobes were phosphated
and the whole cam was oiled up & sealed in a bag
I assume later cams were just completely Phosphated ?
your cam looks to be all black ?
may be worth checking with thinners that it hasn't been painted with matt black paint , before fitting
not saying it's a bad cam , may have just been painted to temporally protect it