This electro etching is an industrial process? Or something one could do with basic chemicals and a power supply? Like a battery charger maybe?
If you do web search you'll come across a bunch of instructables that apply to this that are probably going to explain better than me. Small etching can be done with a battery, a charger or other DC power supply would be needed for a chunk of metal this big.
I used a 24v power supply that has a max 3 amp output. Tape off the region around the design and clean all paint and rust etc from the design area - I used Gorilla tape but any insulating tape that can withstand a long soak will work fine. Other material might work better.
I made a cylinder about 3" tall around the design using a plastic bowl with the bottom cut out, taped in place and plumber's putty pressed into the seam on the inside to make it watertight. You could also wrap the entire rest of the KB with non-conductive material and completely immerse it in a bath - I chose to just do the design area.
Fill with salt water - I used about 1/4 cup of salt to two cups of water.
Where the paint was already missing on the handle I attached a few wraps of copper wire and this runs to the + terminal. The - terminal wire went to a large steel washer suspended from a piece of plastic into the water but above the surface of the bell.
Put the entire thing on something non-conductive and turn on the power supply. The water around the washer will begin to bubble and the water will turn sludgy and discolored. To get even that shallow etch took 12 hours with the power supply full on at 3 amps.
I have done designs on knife blades and small name plates and such and it usually takes minutes, not hours, so the mass of the KB makes a difference. This was on my 50 lber, a 15 might go a lot faster, a 32kg longer etc. Smaller designs, larger, YMMV. I initially moved the location of the washer to make sure the etch was even but I don't believe that was necessary (I used to do some hobby electroplating and the location of the anode + material was crucial to getting a good even plate, etching maybe not so much).
Its interesting that the etched area became smoother than the cast surface I began with.
I am planning to do one with a lot more detail (pine cone with a couple of branches, lots of fine line detail) and fill it in with brass brazing rod. The way I see it these are lifetime fitness tools of a personal nature. I wouldn't decorate my favorite 45 lb Olympic plate or 50 lb hex dumbbell, but my KBs are a different animal. With a nice etch decoration they become an heirloom.