Hi,
There is only one model of ASA5505 with different licensing, softwares and possibly modules.
If I would have to guess then this V11 refers to some sticker on the unit? (don't remember if the ASAs actually had this) This probably just refers to how new this model of ASA5505 is. When it was manufactured perhaps.
Atleast some of our common used Cisco Routers have stickers on them with different such codes. For example some of the bit older ones had for example V04.
Don't really know what the case is. Have never put much thought into it.
- Jouni