How Was This PCB Made

Bit of an off topic question today, but I assume one of you electronics guys would know.

I took apart something today to find a rather interesting PCB.

Its black with very shiny traces. If you touch the traces they are very thick feeling, raised above the black part. There are some numbers on there that are very tinny so I don't guess it was one that was chemically etched like you would do at home. And the black area doesn't show any signs of a mill cutting away the unneeded lines.... so any idea's?

Also can anyone tell me why some of the pads are round and the others are square?

It looks like a standard pcb to me, no solder mask, and the tracks have been tinned.

I use a square pad to indicate pin 1 so I can attach polarised connectors the right way round.

You can add tin (or gold or whatever you like) to traces after etching.
One way is to put the components in place, and then have the PCB take a solder bath (googleable).
A more tidy way is to do electrolytic tinning.
That's a similar process as goldplating.
I remember seeing some powder you needed to solve in water and put your PCB in to get this going.
But that's been a long time ago so i don't know exactly how that was done and what else you would need.
I'm also not that sure that what i saw in those catalogues was what i remember now...