Mine has the size etched in the cavity, I did deepen the etching a bit to make the size more prominent. My first mold was homemade and I used a ball nosed 3/32 punch to poke a dot in each side of the mold kinda like a raised eye, 1 dot on each side of the 1 oz, 2 dots on each side of the 2 oz, etc,, etc..
Lines are good, the dots are easy to see, easy to feel in low light and being on both sides of the head make it easy to find. Plus, if you are really creative you can color the dots for visibility.
I tried ink stamping but as the lead ages it gets darker and makes the ink blend in.
Alternately, you could powder coat each size a different color. I did this for a friend some time back 1/2, 3/4, 1, 1-1/2, 2 ouncers. He went with yellow, blue, green, red and purple for his biggest one. I actually like his system. Colors are much easier to see and makes selection a breeze.
Nothing fancy with the PC, heated the lead, actually uses a salt shaker to sprinkle the color on, rotated a few times to get color uniform the held it over the heat gun to get the gloss. I told him it would be best to oven cure them but my oven is too small.
Another option to coloring would be sally hansens hard as nails nail polish. myriad of colors and you could do lots with one bottle. Not as durable as cured PC but pretty darn tough.