Originally Posted by gg1man:
We have to remember that AC motors reverse direction by flipping the armature and field windings...
The motor in question is an AC/DC universal series wound motor. With the addition of a rectifier to power either the field OR the brushes/armature, a universal motor also reverses with a change in polarity on DC. The permanent magnets in a DC(can) motor simply take the place of a DC powered field.