There are different models of Rem 1100 20 gauge guns
There is Standard Weight, LW and LT
Please ask him to verifly which model or you can ask
him to tell you the last letter in the serial number.
Once we know that, t'will be easier to provide a route forward.
Should be an "N" or a "U".
Mike

p.s.
http://www.remingtonsociety.org/forums/viewtopic.php?t=21861