Hello Cat MWP! 
You say several boxes of calibrated instruments. Is this just a note on the outside showing a general status?
Is there another sticker on the instrument itself?
If it is a just a general status, then no biggie. If that is the only sticker, then I don't know.
A user should be able to easily ascertain the applicable information regarding an instrument's calibration status. Primarily, is the instrument fit for use. If there is no other mechanism (instrument list; whatever) to determine an instrument's current status, then a calibration sticker on the instrument itself would be in order.
Now, if the only sticker in that case is a Post It Note, then I say no-go. First, that sticker does not have any unique information. The stickers (and/or box; and/or instrument) can get switched.
To me, I should be able to pick up an instrument (not just a box) and know it's current status; either through a unique marking on the instrument, or a list showing status by serial number/unique ID number.
We have small instruments that we have to affix calibration stickers and unique ID numbers to the box they are stored in. We have a lot of problems with instrument boxes switched, lost, etc. IMHO, it's always best to link to a unique identifier on the instrument itself.

Our Calibration Coodrdinator has affixed Post-its to several boxes of calibrated instruments with "Calibrated OK", the date and her initials. Is this an acceptable method of labeling?
Is there another sticker on the instrument itself?
If it is a just a general status, then no biggie. If that is the only sticker, then I don't know.
A user should be able to easily ascertain the applicable information regarding an instrument's calibration status. Primarily, is the instrument fit for use. If there is no other mechanism (instrument list; whatever) to determine an instrument's current status, then a calibration sticker on the instrument itself would be in order.
Now, if the only sticker in that case is a Post It Note, then I say no-go. First, that sticker does not have any unique information. The stickers (and/or box; and/or instrument) can get switched.
To me, I should be able to pick up an instrument (not just a box) and know it's current status; either through a unique marking on the instrument, or a list showing status by serial number/unique ID number.
We have small instruments that we have to affix calibration stickers and unique ID numbers to the box they are stored in. We have a lot of problems with instrument boxes switched, lost, etc. IMHO, it's always best to link to a unique identifier on the instrument itself.
