I contacted them. They replied:
"Thank you for contacting Remington! According to the serial number provided, your 870 Express was manufactured in 2013. You can no longer go by the letter suffix, as these have been reused over time. The barrel will be roll stamped with the correct shell size."
http://i349.photobucket.com/albums/q378 ... bbbiih.jpg
http://i349.photobucket.com/albums/q378 ... ka02zb.jpg
Here are the links to barrels photos. But I have no idea how to identify letters. Probably it's just scratches )
