Congratulations, great find! 
I have a feeling the bag may be a replacement, though - I have a manual for Model 305, and it shows the cleaner with a different bag design. Since it's worded 'The Hoover Special', I'd suggest it may be a Hoover-Factory rebuilt version.
Jeff, it's interesting what you say about some being made from aluminium and some from stamped metal; my list of serial numbers shows Model 27 was made in both steel and aluminium, but it doesn't say that for Model 305. It could be an error in the listing, or perhaps they just didn't bother to change the serial numbers when they changed the material. It also lists 305 production dates as 1938-45, with 379,623 made in total.
