Ed,
Keep in mind the Lux in the ad was a rebuild, and the ad was probably from the 40's or 50's. There was also a place to insert the name of the vac store offering this promotion, and I'm thinking that the rebuild company (probably Metropolitan) probably included the ad cut when the vac shops ordered a certain number of units.
You probably also noticed a GE and a Kirby, think it's either a Classic, Omega, or Classic III. Glad you enjoyed them!
Jeff