I don't think it has to be the manufacturer of the seals. I think it is more like a store that sells the seals. (It's possible that the seals could be manufactured at the store, but it doesn't have to be that way.

Yeah, this is a bit tough because at least in English, there are no such stores because we don't have those seals! That's why I put "signature" in there so that people can have some idea of what kind of seal it is.