How can I identify series 1 modules?

Im newbie to this XBee modules. I borrowed some zigbee modules (MaxStream rev:11) for testing with ConnectMe 9210. I find out that I have to use ZNET 2.5 stack which I cant upload to module (it reports: Incompatable modem selected for programming). In this forum I found that there is two kinds of XBee modules - series 1 and series 2. How can I determine which series I have? How can I buy series 2?

And one more question what is difference between ZNET 2.5 stack and 802.15.4 stack?

Thanks Jirka

The big difference between 802.15.4 and all the other models is that with 802.15.4, if one XBee wants to send
a message to another, they have to be directly in range. All the other models allow messages to be relayed through
intermediate XBees, which means you can then set up a network that covers a much larger geographical area.
802.15.4 is a firmware version that runs on the Series 1 hardware.
ZNet2.5 is a firmware version that runs on the Series 2 hardware.

The following link gives you clear picture of different types of XBee modules,