We use one piece "calf" tags. Blue for the boy calfs, pink for the girl calfs. They are numbered in order behind the year letter. We also have a small enough herd to run numbers in order. When we get to 999 we will have to start over at 01. EX. if my last calf of 2012 was registration #15 for me, its tag would have Z15.On top of that the sires #, on bottom the dams #. So when I am in the pasture looking for a particular calf, the first thing is the tag color. Then the sire and dam #s help me be sure its the right one.Mostly this is handy when visitors are here looking at the herd. It can get confusing if you have multiple ET calfs by the same donor. I may be able to say well this calf goes with that cow, but its an ET on a recip. The sire and dam on the top and bottom remind me of the mating then. We keep all of our records on paper, and on computer spread sheet as well as the Association registery. So, last calf of 2012 may have been Z15, first calf of 2013 may have been A16 etc. If you use the letter system a while it will become second nature remembering the year that goes with the letter. 2016 letter is D by the way..