Odd? Don't they have state the re-test date or something normally? After all, the whole point of the sticker is, as I understand it, to show testing has been done, and when a re-test is needed.
Ah, but hang on - here it is under a flap:-
So what's that flap for? Oh! it is removable:-
And leaves nice sealed glossy finish that you can't alter:-
And the whole thing seems to be tamper evident:-
They are probably expensive stickers. Why go to all that effort to copy serial number on to them, and then not peal off the backing and stick it down?
I can only hope that the whoever it was knew more about working the test equipment than the stickers!