first, you must can input 2 bytes character like Korean, Japanese or Chinese into chat window in D3 client if you want to use this exploit.
I'm Korean so I'm using Korean localized version. I'm not sure this exploit can use in English or other language version.
1. open chat window and input any 2 bytes character (I'm use ㅇ character)
2. link any UNID'd item
3. click between 2 bytes charater and linked item name
4. press delete key 2 or 3 times then you can see the item code
(do not press enter key this step. it may crash D3 client)
5. press ctrl+a then press ctrl+x and then ctrl+v in text editor like notepad
you get a code like this.
⻈Item:2,1565456761:-146123031:1055553278,1055553278,1055553278,1176553157:-1:0:-1:-1:-1:8:523:523:0:0:6:0:-1144451098:|h[가시 투구]|h
then you can know rare quality of UNID'd item now.
0:0:6:0 - 4-affix rare
0:0:7:0 - 5-affix rare
0:0:8:0 - 6-affix rare
next, this item code has 3 different type.
1. UNID'd code ingame
|HItem:2,1565456761:-146123031:1055553278,1055553278,1055553278,1176553157:-1:0:-1:-1:-1:8:523:523:0:0:6:0:-1144451098:|h[가시 투구]|h
2. UNID'd code in lobby
|HItem:2,1565456761:-146123031:1273837477,-2012337763,1951515674,-334812892:-1:0:130756:9:8:8:523:523:0:0:6:0:-648496672:|h[가시 투구]|h
3. ID'd code
|HItem:2,1565456761:-146123031:-334812892,1951515674,-2012337763,1273837477:-1:0:130756:9:8:9:523:523:0:0:6:0:1941137377:|h[가시 투구]|h
did you see that? UNID'd code in lobby and ID'd code are perfectly same except final number.
final number used for integrity check of item code and item ID'd state I guess.
so you can link and get exactly stats from UNID'd before ID'd if you discover formula of final number.
credit to 제피아스 of diablo3 inven