how rare is this?

When I made my dark thorn shield the UV that I got with it was increase elemental defense: maximum. How rare is this and how much do you think I could get out of it once I can unbound it?

Okay sweet. Im gonna make it tier 5 soon too.thanks for the info
Once you unbind it? How do you unbind an item???
It's suspected that there will soon be an "unbind" shop where you can unbind items to sell/trade with other players.
Which is silly to suspect. Because what's the sense in items becoming bound, if you can just unbind them later on whenever you want. Even if there's a fee, it still seems counter productive to what the devs intended. Anyway, as has been said, it's extremely rare, and you're extremely lucky to have gotten a UV on it. Some people buy and craft this shield many many times, before they get a UV at all. Getting a very good UV on it is even luckier.
Umm Malleable - http://forums.spiralknights.com/en/node/8737
"Over the next month, we plan to implement a new store that will allow players to "unbind" items. There will be a fee for doing so, roughly equal to the cumulative cost of crafting that item."

only problem, i think there will be items - such as boss token gear that will probably have a block against unbinding. I mean c'mon preview testers can't just go around unbinding groundbreaker stuff right? however keep your hopes up ;)

I think you'd better keep that shield to yourself since it might be really useful (unless you want to make a fortune). Yes, a Maximum UV is incredibly rare, the highest UV I got was a Medium. That shield will be really useful in RJP since the enemies there deal Piercing (Jelly) and Elemental (Construct).
You can't unbind an item once you bound it but there will be a service to unbind items soon (hopefully).

It'll probably be where Non-Craftable items can't be unbound. You will be able to unbind Avengers, Fausts, Silversixes, Blackhawks, etc.
You probably will NOT be able to unbind FoVs sadly since it is a Non-Craftable item. On the other hand, you'll be able to unbind CoAs and the upgraded Snarby stuff.
Getting a UV on a piece of equipment? About 10% chance. Getting a maximum defense of ANY kind on a defensive equipment is very, very rare. If you got it unbound, I wouldn't be surprised if you made several tens of thousands of crowns given how popular that shield is among swordsmen.