The DS-KD8003-IME is a Generation 2 IP intercom. There is currently no A or B versions for this model.
The Gen 2 IP vill intercoms have A and B versions. The A versions are EOL and if you are looking at these you should get the B version moving forward as there won't be any updates for the A versions. The B versions also support the newer Security 2.0 protocol of later firmware, which is what most Gen 2 intercom components appear to be shipped with now. Therefore if you get an A version villa station it may not be able to communicate with hardware running Security 2.0 firmware.
The DS-KD8003-IME will run Security 2.0 protocol in its latest firmware.