On Fri morning I mailed off  2 swap books using the PBS DC.  I'm in Wa state. Both were going to the East Coast. One book has already been delivered and the other one hasn't left the state yet.  I just think this is funny when they were both dropped off at the same time using the same postal rate: both MM. 

Weird.

I found it quite amazing when 5 books I sent from here were scanned within seconds of each other through the sorting unit 5 hours away. It was a day or two later. How'd they all stay together??

Media mail can be so weird.  Not long ago, I mailed out two books at the same time, both MM and both with DC.  One was going to TN, the other to CA.  I am in Oregon.  Oddly enough, the TN one made it to its destination several days before the one going only one state away to CA.  They were both scanned in Federal Way, WA on the same day, so whatever held up the one going to CA happened after that.  Some media mail sorting centers must be more efficient than others, I guess.