I have a generic 60Ah battery in my car. It seems to work fine. Was installed by a kind of semi-shady shop, but has worked fine for over a year.
A more "reputable" shop looked at it and said "That battery is too small for this car."
The brand of battery is an Israeli brand, so I don't have perfect information on it. For example, I can't tell if it is a G35 size (and I am not sure I care if it fits in the battery well and is held down securely?).
The battery is: Volta 34856093 / 60Ah / 420A-IEC / RC 100 Min
This is the page about the battery model (but the actual battery does not have recessed terminals the way this picture has, fwiw)
The car has no observable problem related to starting or running.
Should I take action or leave it alone?
(I notice it was installed without grease felts under the terminals, and some fur is starting to grow... I can solve that easily enough... a hazard of a penny pinching shop.)