Like all artistic endeavours, the subject matter is open to artistic interpretation by the artist creating the design. This was true of ancient cultures as it is today.
Perhaps the biggest difference is that today we have far more research material and a wider sphere of influence to call upon than the ancients did. But both share the same common theme that has been carried on for a millennia of artisans of all cultures, and that is to create objects of outstanding beauty that can have practical and/or spiritual meaning to the society they live in.
Hand engraving is a highly refined and skilled art that has changed little in the last few centuries. The artisan cuts lines in the metal using small, sharp, steel hand tools called 'gravers' that are forced along by hand or a slight hammering action. To do this the engraver must develop an affinity with the metal they are working on whether it be steel, copper, brass or precious metals like silver and gold.
Today's engravers have the benefit of better magnification like microscopes so the work can be incredibly fine. They also have better steel gravers as some of the metals to be engraved like stainless steel are extremely tough to cut through.
First the design is roughly drawn out with pencil and paper and increasingly refined until the final design is reached. After that it can be drawn straight to the metal or transferred by various means to the item to be engraved. The main lines are then cut into the surface.
For more high end and sophisticated work, the background is then relived which involves the cutting away of the background to below the surface level. The background is then textured in some way to make a contrast between the surface design and the background. This texturing is an integral part of the overall design of the engraving and has to be balanced in harmony with the overall design. Too much background dominates and too little will overcrowd the work.
Finally the shading, or detail cuts are made. These tend to be lighter than the main cuts and add shadows and contrast to the overall design. It is at this stage that the personality of the work shines through. Quite often the engraver will just make it up as they go along and it is only then that they get to see the real beauty of the metal and design that lies within the engraver's imagination.