Works but polarity reversed

Polarity was wrong - what was not a problem for me because I have the battery simply resoldered.
A note to this was not on the package with me.
Have it but immediately knew one thing because the original battery was different rum plugged.

Update 04/03/2015:
More than a year has passed - the battery still works without problems.
Seems also still the same power as to have at the beginning.
(Baby monitor is in use every day for the change)