I've heard it used and use it in conversation, occasionally.
It's an acknowledgement of a mistake (usually an obvious mistake). A correction. Think correcting an autocorrect fail, like some people use *. That's how I (and some others I know) use it - in this context, not as the mathematical concept of odd vs even.
Edit: I found a couple of examples in my text messages. One time, I was telling someone how far off I was from meeting up with them and said that I had just passed "Swanson" Street (in Melbourne). This was a typo, and I immediately corrected, as soon as I saw it, with "Swanston, even". In this sense, it could also be used as a synonym of "rather" or "actually". Another time I commented on "slightly weather", which I corrected in my next text as "slightly warmer weather, even"
Interesting, I've never heard of that usage. I guess it's not American English.
Snagglepuss used it that way (sort of*).
cite*wiki describes it this way
...but I'm not 100% sure what all that means.
