closes Dan Kennedy / GKIC style
P.S. If you're still reading, it tells me something. You're not the type to ignore an opportunity — you're the type who acts.
The P.S. as a standalone close is a 1920s trick that still works because of how the eye scans a page: headline → P.S. → body. This P.S. sells the identity ('you're the type who acts') before the reader has even read the letter.