Discuss Anonymous's answer to: IRS Form

This is the code used by the IRS for a 9½ tall by 12½ wide, 32 lb. light brown kraft window envelope.

I'm holding one in my hand right now.  On the front lower right quadrant there's a 3 ¾ tall by 5 3/8 wide plastic window to enable the display of an address on a page placed inside.  On the reverse side, there's a contact seal strip along the long edge at the top.

The following appears on the envelope's reverse side at the lower right hand corner:
E-182 W (REV. 3-2000)
Cat. No. 64288W