Just a tip, though one calibration weight I am pretty sure works across the board when digital: there's lots of little things around you can use to check the weights we normally use. For example, any US bill (like a dollar) is 1 gram.
I have an expensive OHAUS N12120 I got from the pile of broken scales at school (back when I went to school). Just needed a couple leads inside resoldered! But my point is that a buddy of mine got a 10mg palm scale (like yours) from a smoking accessories
store, and we spent about a couple beers worth of time measuring junk around my apartment. They are pretty much the same -- if you breathe on mine it changes the weight (seriously) but they settle to the same. In fact I have thought about downgrading just to get the space back on the counter I keep my nerd stuff.
HTH