Sorry about that last message - new to the forum! What an amazing and interesting thread this is. If i can add a few points...
The wattage of the 502 was 425, the 504 was 450. The replacement cleaners for these were models 506 and 502s, with wattages of 550 and 500 respectively. The 506 was out a little bit before the 502s. Newer versions of the 502 had the long plastic strip down the front but I have no idea why they didn't all have this. When the 550 was launched, the 506 became a 560, with a 560 watt motor. It was suggested here that a 505 was avaliable in UK, but I have never seen it. All I have seen is a picture of such a machine, same as the 504, but made for another country. The mustard coloured hose and dusting brush in the pictures in this thread were sold here in the UK but only on the earliest machines, where a deluxe tool kit was made for the 504. As no other Electrolux cleaner had these colours, I suppose it was easier and cheaper to use brown or white, as indeed they later did. Not forgetting that not all cleaners had the tools supplied with the cleaner, therefore it is quite common to see a cleaner with what you might call the wrong tools...tools which were earlier or later than the cleaner they are seen with, depending on when they were bought and what kits the shop had it stock at that time.
According to Electrolux, the 506 was originaly supplied with a woven hose and it would have been the last to have this. The 502s had the most basic of all hoses, with no handgripping or suction control. It used a thin white concetina hose, thinner than on cylinders, but was still metal when it came to tubes. This was the first tool kit to dispence with a floor tool. Later on the tool kits changed to white plastic, when the 550 and 550 came to be. These kits were used on the 550 and the 560 until there was a switch to brown, round about the time that the 502s was finally taken out of production. Again I believe the colour change of the tools to be down to ease, as some of the Electricity Board cylinder models were using the same brown tool kits whereas no other had white.
The 500 series was subject to countless minor tweeks over the years, with additional mouldings being added to the design to improve strength on the weak points. The very last 502S, 550 and 560 were the most solid of all as they contained all the modifications which Electrolux had added since the start of the 1970s.
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