|Just in case you had trouble getting hit.|
Unfortunately, "Bullseye" is a fairly useless shield. If you're looking for more SH in exchange for EV, then you should probably just upgrade to a large shield. Only kobolds and halflings might consider wearing this, and even they probably wouldn't: the SH increase is really not worth the EV penalty, especially considering that plenty of non-artefact shields offer useful resistances.
In earlier versions, Bullseye used to be a buckler.
Bullseye was removed in 0.14.