I don't think it's printed, the surface is too smooth and there's no sign of any flash that needs removing.
I've spent a good while looking at it and comparing it with my other magazines, apart from capacity they appear identical. Yet no matter how I insert the magazine, press it in, snap it in, pull forward/back, twist it.........the spring doesn't 'click' and the magazine falls away.
It's also a bit frustrating that the (business) seller doesn't answer their phone.