I just heard back from Bram this morning. The Vespa 150 I am getting is a four speed. He confirmed that the 150 Super badge on the rear is only that - a badge and not an indicator of the model (I'll probably be looking to switch that). He also wrote, "Your scooter is four speed. The manual book what I got only using 3 speeds. But almost similar with others. Some of Vespa 60's has 3 speeds specialy for VNB and VNB type but for your scooter is 4 speeds."

So, it looks like we're talking a Vespa 150 with Vespa 150 GS capabilities. All this was a relief to learn! Tomorrow will be two months since I purchased the scooter. Hopefully the next day, it will actually be here.