The green vac is being sold today as a commercial model (As far as I can tell, this is a Perfect clone of the Discovery)

same interchangeable parts for the most part (Type U bags is one give away, even though the green one does not specifically say so. The red one is now discontinued.

Any guesses? these are specific models.

this basic design dates back almost 30 years now.

I believe the green machine pictured is a Bissell incarnation of this design. 

Very good design, very good cleaner.  I used mine just last night that I bought a few years ago from Kirbyloverdan.

Well before I forget ...

If you have the parts lists for these specific models, you will find they share many of the same parts.

I believe the Sanitaire was under the Eureka badge for a while (now Electrolux home care products - the new Electrolux, not the older Aerus/Electrolux)

I believe Aerus/Electrolux missed a big opportunity. At least with Perfect and others cloning the classic machines, we can keep the older vacuums going.

My response was deceiving.  I was not speaking of the Bissell machine as it appeared I was.  

I have a Lux Guardian Upright, and was speaking to the design it shares with the others as being a good design that has been around awhile.    The lux is a good cleaner, and appears to do a good job deep cleaning and grooming the carpet.  

Here is another one. 

these models are good for reference, since parts may be cheaper than ones that state "for Electrolux upright"