Chemical milling, chemical etching differant name for the same thing. It could be done the normal way but it would be pretty fiddly with the material only being .25mm thick and quite easily picked up. I dont have a problem doing it but it looks like the etching process is the way these things are normally made as well as making a nice job of it. I know from milling pcb's what a horror doing very small stuff is though. I may of understimated the cost of etching yet so may end up milling the piece.