You might actually be thinking of hankos, which are widely used in every-day paperwork, and they are usually a personal seal rather than a family seal. I don't

You might actually be thinking of hankos, which are widely used in every-day paperwork, and they are usually a personal seal rather than a family seal. I don't think they're high culture, as almost everyone has one and they're used for day-to-day document signing of many types of documents, like opening a bank account or filing taxes and so on. They're also part of some important business practices. One such practice called nemawashi, which is a "peer consensus" required for big decisions in some companies. A document outlining the change or project you want to undertake circulates to all peers or superiors it would reasonably affect, and they must all sign with their hanko in order for the process to be accepted. Although there are some high-culture elements to them, such as having a bigger hanko if you're in a higher position in the company, some etiquette around hanko placement on the page depending on your rank in the company. There is also a tradition of giving a fancier hanko as a coming of age gift, those used to be of ivory (and still can be, Ivory in Japan is a fairly fascinating topic in itself).