I have a set of pipes I believe are Stout 4" Slip Ons but the stamp on the pipe is "027-6523" and under it is stamped "28213". That doesn't match up with what I can find for any part numbers. What are these?

I have these on a 2007 Road King Classic (Stage 1 Flash / K&N High Flow / Stock Head Pipes). They sound great (replaced V&H Ovals I've had on it since new) with a nice rumble.

Thank you.