Browser Plugin: USPS with No Postage

Hi,

What is the value of the Carrier input value for ShipRush USPS with no postage?

For example, with Stamps.com, it is:

nntp://ship?Carrier=Stamps...

For Endicia, it used to be:

nntp://ship?Carrier=Endicia...

Also -- where can I get the latest documentation for the plugin?

Thanks!