Forever Stamp On Penalty Envelope

Here's one I recieved from the SS administration a couple of months ago. I am thinking what's up with this? Any thoughts on why? Just curious.

Well it IS the government. Need I say more?

I don't know the exact rules, but I'm pretty sure it has to do with whether the inscription in the box matches the location it was mailed from. It looks like it was mailed from Pheonix.

Either way, they aren't actually paying for the postage twice. When there isn't a stamp, it gets tallied up by permit number. Since there is a spray-on cancel, that means the machinery recognized there was a stamp on it.

Wow, a stamp on a piece of mail from the government. I haven't seen that in ages. Also those spray on cancels make such a mess. They are never clear, looks like a blotch of ink. Just my opinion.