In all honesty, that vacuum is worth only what someone is willing to pay for it. That is an opinion shared by many collectors on this site.
That is a nice specimen of a Guardsman that you have, however I'm sorry to say it's not worth tons and tons of money, so if you're looking for a lot - prepare to be disappointed. Granted, eBay is funny, one day something could sell for $25, and the next day it could sell for $200, but don't get your hopes up. If you had something NIB, that's a different story. I wouldn't hope for more than $100.
Contrary to what others have said in another thread of yours, I don't find that model to be particularly rare. Granted, in nice condition they're becoming less and less common - but that doesn't mean it's rare. I've got one in my collection, and know of quite a few others in other collections. Yours does looks to be in nice shape, with the original bag and original cord... however I believe the headlight lens has been replaced; the one on my machine says "Guardsman" on the lens. I've also seen this model with and without the Hoover Medallion on the base, I wouldn't say one is more or less common than the other.
Put it on eBay with a low starting price and no reserve, and see what happens. That's the best advice I can give you, and that's what I would likely do if I was in your position. Hope that helps, good luck!
