Well. They opened the package at Limbaugh’s house:

The package was sent by a man in Pennsylvania as a “business opportunity” for Limbaugh, Hess said. The man was not identified, but when authorities called him he apologized, Hess said.

The package contained an electronic plaque commemorating the assassinations of Abraham Lincoln and John Wilkes Booth. No further details about the plaque were immediately available.

Looks like a fellow wingnut sent him this.

From: Bomb squad called to Limbaugh residence