An inductive argument is strong if there is more than a 50-50 chance that the conclusion will follow from the (presumed) truth of the premises (Hurley, 2000). Otherwise it is weak. The presented inductive argument is strong because the conclusion (the ring is probably made of 14 caret gold) is based on the (presumed) truth of the premise (small print reading ’14 caret gold’ on the inside of the surface of the gold ring). The seller is a trusted jeweler, indicating that the premise may be true. The argument would only be weak if the conclusion was definitive (something like ‘the ring must be made of 14 caret gold’).
Hurley, P. J. (2000). A Concise Introduction to Logic. Belmont, CA: Wadsworth.