Why are these cam pulleys constructed differently?

Question

I am about midway done with changing the timing belt & water pump on my 99 Toyota, which features a 6-cylinder 5VZ-FE engine. After getting the front timing cover off, I noticed that the passenger-side cam pulley has a raised rear lip, but the driver-side pulley does not. What is the reason for this difference?

Passenger-side cam pulley, with raised rear lip:

Driver-side cam pulley, without raised rear lip:

Answer 1

The raised rear lip is used to align the timing belt. It only needs one of these to keep the belt aligned, thus the difference.