Series 5 had an 86 degree slider trigger - Series 5 Basic has a basic .45 dergeee hinge.
S5 had a deluxe kit - S5B - Basic.
S5 had a hole drilled in the VRA - S5B was hole-less.
S5 had 'Series 5' and 'CCM' lazered in both sides. S5B had Series 5 Basic on one side.
S5 had a CCM lazer engraved feed band - S5B had Series 5 Basic engraved on the band.
S5 came with matchin barrel in .690 insert. S5B was barrelless.
S5 came with a delrin (farty) pin in the valve - S5B had an upgraded valve pin.
There are a few other screw dimension changes - but probably not worth mentioning.