Q and 66 are two different models. The Q employs a clutch mechanism that allows the siren to "free roll" long after the motor has stopped turning. As with a brake option are designated in the full model name, i.e. Q1B or Q2B. The Q1 is painted whereas the Q2 is chrome with a chromed motor housing (Q1A and Q2A designates no brake). The 66 is the chromed version of the model 28 and has a smaller diameter than the Q. As it is a direct drive without a clutch, no brakes were ever used as the siren tends to wind down rather quickly. (The G stands for Grill with no light). It is not possible to add a brake as the siren stator (outer housing) does not have a hole for the brake plunger and I would not recommend your friend attempt to create one!
