Gauge Designation

[ckchastang]

I own a 12 gauge 870 Express with a 26 in barrel with the prefix letters CC which is most likely April of 2008 since it was bought brand new as a gift in 2014. It also has F as a suffix, but from what I have gathered no longer means anything. Is there any other way to tell if it is chambered for mag or super mag? There is something stamped on the barrel that could be S1 or SL. The stamp is poor and hard to read. On the inside of the barrel (which can be seen through the receiver) are the letters REP with a rectangular border. Thanks for any help.