My old Rem 870 .28 ga is marked MOD that I bought in 1976. I used to brag that it killed everything at any range. However when I miked it the choke turned out to be a .007 choke which amazed me.
The moral of the story is don't believe the markings on the barrels until the chokes are actually measured.
Check out the choke data and ranges below:
http://www.hallowellco.com/choke_chart.htm