When I'm trying new 9mm loads, I load 10-15 of each into Glock mags and label the mags with a label maker. But that only works because I have a lot of Glock mags. Otherwise, I may either put them in an MTM box, a row of ten for each load and scribble the row-by-row contents on the lid with permanent marker (wipes off later with alcohol), or use labeled baggies.