FastMover,
The badging you described is that of a 2001-2003 Prius which had a sedan body style as opposed to the hatchback style of the 2004-present Prius. 2004 is also the first year Toyota's used the HSD badging. The top badge you were unable to read was "Toyota". If all three Prius in the convoy were of the 2004-present body style, then I can only guess that the owner of the car with different badging ordered & installed the 2001-2003 badging because they liked it better.

Christopher
2007 Gray Camry Hybrid, 14,000 mi
2001 Silver Prius, 93,000 mi
St. Louis, Missouri