My understanding is they scanned actual coins to get the computer image they used to create the master hub. Of course they changed the date on the image in the computer. I don't remember where it was but there was an article or a video on the subject and they showed them scanning one of them.
I think it was the gold merc thread where @dcarr described the method they use which if I remember correctly does start with a computer based rendition. Even if it was a scan though with the technology available today they shouldn't have had any problems picking up the details and like you mentioned should have had the foresight to clean up anything that was missing