An identifying coding apparatus employing modulated reflectance technology involving a base station emitting a RF signal, with a tag, located remotely from the base station, and containing at least one antenna and predetermined other passive circuit components, receiving the RF signal and reflecting back to the base station a modulated signal indicative of characteristics related to the tag. In particular, one of the antibodies is labeled and each of them binds specifically to a different site of ciguatoxin CTX3C. Furthermore, each of the internal stud and the external stud may be created from a cold-rolled steel. A filling and pressurizing means pressurizes the annular space.