This polka is in G Major, so when coupled Paddy's Polka (no. 1), there's an interesting key change from D Minor to G Major..
In this tune, the B part can begin on either a G Major or E Minor. Tony's preference is for the E Minor, so that's how it's notated in the booklet (Book 3).
Listen to the lesson (PaddysPolka2.mp3, 7 minutes 37 seconds. xx MB)