That Hoover Special looks like a 102 or 105 with a Robbins and Myers motor. The switch is on the right (from the back) which would be 102 but it looks like it has the tilting bar on the bail which would be a 105.
Stopped at the Goodwill in Mundelein, in among the vacuums is a Kirby Sanitronic 50 with the Kirby logo that lights up in the headlight hood for $9.99 and I'm thinking Darn I already have one of those. So I left it there.
If it looks like this it's a rebadged Royal, mine is a 1950 Packard model.
They were a premium when you bought a Packard, you had a choice of several different appliances i.e. a single door refrigerator, a vacuum cleaner, a sewing machine, etc.
If you look at the rear bearing you will notice a cap over the bearing held on with two screws. If you unscrew the two screws the cap will come off and you can add grease to the bearing. The front bearing is the same BUT you will have to take off the fans. To get the fans off you will notice...
Looking at my 102, 105 and 541 handle bail
The 102 is different
The 105 and 541 look the same
The only difference between the 541 and the 543 was
the 541 had a brushroll and sateen bag
the 543 had an agitator and black cloth bag
If you take the control valve out and unscrew the knob I'm guessing that the plastic around the O ring has broken off and the valve is leaking. You can still get the new knob/control assembly from your local Aerus dealer.
Ben
I have a G4 and yes it was the last model to use Phillips screws. It also shares the brush roll with the G3 so the wear indicator light is on the left when you stand behind it.
The lavender color tape for the bumper
Just so you know I was helping Scott at Tinley Park Kirby and he has a whole roll of the tape for the G4 bumper. It still has 5 stripes left on the roll.