While riding my bike, I saw the this board in the street. It looked like a Fastrak transponder so I picked it up.
There are a couple interesting notes. The board is labeled “TIRIS” (Texas Instruments RFID Systems), which explains the new company name, “SIRIT”.
In the older model, they used a custom Atmel chip instead of the TI MSP430 now in use. They probably moved to the MSP430 to save money. There are significantly less analog parts on the older design, which means more of the demodulation may have been done on the custom chip. There are two clock crystals instead of one. The buzzer was attached with external wires, not traces.
You can see a teardown of this same model but in nicer shape here. It looks like the 0006 model was both a cost reduction and generalization of the 0004 model. It would be interesting to look at the firmware of the Atmel microcontroller and see how it differs.