I have a similar story regarding my 2003 unit which contained appliances with a 2002 manufacture dates and a 2003 model title. There is also a plate on the curbside that states it is a 2003 trailer and the first owner said he bought it in late January of 2003 got a title printed in February. Just like automobiles, trailer model years don't match calendar years.
For almost 15 years I was told Airstream hadn't made a 2003 Safari SO model until we formed the slide out society on the forums and then three appeared among the replies for membership. It was at that time that the 2003 Safari SO option was added to the forums selection list. Soon after that, I found a digital copy of a marketing brochure that showed the Safari floor plans.
If you check the Airstream site for old manuals, sales materials, and specification sheets for the 2003 model year, the 28 SO model and three variations of the 25 are depicted on the sales brochure but there are no 27 models in any of the Classic, International, or Safari trailer lines. Here is a link to that brochure material:
Apparently Airstream is not the most reliable archival source for what was built when and their serial numbering only matches production dates/sequence and not model. On the other hand, your title could also contain a typo that got entered with a new owner's re-issued paperwork.
Maybe it could be an extremely early 2004 28' Safari W model.