A small label maker costs around fifteen dollars online. I mark every vial as soon as the kits arrive.
Just got my storage containers and trays this morning to begin keeping peptides in the freezer. Trying to figure out a good way to identify everything inside them. Up to now I've kept them in a dark spot in the original packaging and only marked after mixing and filtering. Don't want to waste good labels on vials that will be discarded after mixing. Sure others here have useful suggestions.