It has two timebases, which allows delayed triggering.
Electrical difference to 545
The high-voltage circuit is not identical to that of the Tektronix 545A. Neon lamps are used to stabilize the high voltage in brightness circuit. However, the neon lamp stabilizer is often faulty - the lamps aged too fast, with the result that the trace flickers.
Mechanical difference to 545
The mains transformer is potted. Unlike Tektronix instruments of the same era, which require silver-bearing solder, ordinary solder is fine for working on the Lavoie, because its terminal strips have tin-plated steel inserts.