We have a complicated system, but it works well after you get the hang of it. We use several different colors of Z tags on the calves. Each tag has a chronological number on top, which designates in which order the calf was born. Our Spearhead brand is in the middle, and the bottom number corresponds with the cow's number. All of the first calf heifers' calves get a red tag. All of the second and third calf black cows' calves get a green tag. All older Angus cows' calves get a yellow tag. All of the black baldy cows' calves get a blue tag. Solid red cows' calves are tagged with a white tag, and red baldy cows' calves get pink tags.
When we tagged our coming-two-year olds with their permanent number recently, each heifer got a three digit number in the right ear. We also gave the same number on a small button tag in the left ear so hopefully she can retain the same identity if the big number falls out. We also left their original calf tag in the left ear, so we'd maybe remember something about the mother.
If we keep more than a hundred heifers, we still use a three digit number and just use more than one color of tag. All the heifers' calves will get a red tag. If the mother has a yellow tag, the calf's tag will be red, and the bottom number will read Y535. If the mother has a blue tag, the calf will get a red tag, and the bottom number will read B524, etc.
Tags are a nuisance, but it is more of a nuisance not to have them.