A WebmasterWorld thread reports that Google has dropped a search command that used to show a site's pages that were included in the supplemental index.
The command that worked was site:www.seroundtable.com **** -asssdsd but that seems to no longer be working.
The last time I tested it was when I wrote at Search Engine Land, Is Google Gearing Up To Drop The Supplemental Result Label? I guess they were gearing up to drop the supplemental results command and possibly the supplemental results label is next to go.
This is not the first time Google dropped the ability for us to locate the supplemental results of our pages in the Google index. The very old supplemental results check stop working sometime after September 2006.
As Tamar reported earlier this week, Matt Cutts of Google is taking suggestions on what should be the next feature for Google Webmaster Central Tools? One of those items on the poll is a way to list supplemental result pages within the tool.
So maybe Google will drop it from the index and allow SEOs and Webmasters find this information in Webmaster Central?
Forum discussion at WebmasterWorld.

Comments:
André Scholten
07/27/2007 01:09 pm
Leave out the space between the *** and the - and you will see all supplementals.
Benj Arriola
07/29/2007 03:15 pm
Here is a supplemental index checker: http://www.theparadisephilippines.org/supplemental/
Benj Arriola
07/30/2007 07:04 am
I gave the link above, a bug i found is if there are too many pages that are in supplemental, it makes too many queries on Google without pauses and gets but off and no results will be displayed. Thus the tool might be modified to just show the first 500 or less found in supplemental results. Will try to fix it.
No Name
07/31/2007 03:23 pm
Still working but you have to try different command. I tried this one and it's working. site:http://www.computer.org/&