Check the link on the thumbs, see if it includes the skim percentage in the URL for the trade script. Some include it some don't.
Example:
http://www.petiteteenager.com/
http://www.petiteteenager.com/go.php...cip1su b.html
The P=90 in that URL is the skim percentage for the trade script.
Another way is to check the URL to see if it includes a valid link to a gallery.
Example:
http://www.mymasha.com/tgp.shtml
http://www.mymasha.com/thumbs.php?pc.../tm3/l?c=great
The url=http://www.mymasha.com/cgi-bin/tm3/l?c=great shows it's going to the trade script immediately.