If someone buys a silver Kos for kiddush from Jewish owned store (seforim store or silver store that sells these types of items). Does one need to tovel it? With a bracha or not? If the sales person or owner says its been toveled can one believe him?
The obligation of tevillah depends on whether or not the kos is made, up until its final stages, by non-Jews, or whether the final stages of the labor is done by Jews (in which case it will be exempt from tevillah).
If the labor was not done by Jews, there is an obligation of tevillah, provided the kos was once under non-Jewish ownership.
A store cannot do tevillah of the kos (only after the customer buys it can he do tevillah), so that it doesn’t really matter if the sales person is telling the truth or not.