An RF electronic identification system (10) is disclosed and claimed. The system includes at least one transponder encoder (14.1) for writing data into a memory arrangement (52) of a selected transponder (1.1) of a plurality of transponders (1.1 to 1.n) adapted to receive data from the at least one encoder. The system further includes at least one verifier (16) for interrogating a selected transponder (1.1) and to read data stored in the transponder. The encoder includes a controller (42) for providing an identification code characteristic of the encoder to form part of the data to be written into the transponder. The verifier includes computing means (56) for extracting the identification code from the data read thereby and for comparing the code to authorized codes. An indicator (18) provides an indication whether the identification code corresponds to any of the authorized codes or not. A method of verifying the authenticity of a transponder is also disclosed and claimed.