Thanks for the replies above.
My trailer and all the manuals are in storage at the moment and I live in a neighborhood with restrictive covenants. I am severely limited as to how much time I can have my trailer on my driveway for maintenance. That's why I needed to round up all these parts before I begin to take the wheels apart.
I just verified what I need with Justin at Dexter Parts Online (very helpful!) http://www.dexterpartsonline.com
The Airstream part number, for the grease seal on my trailer is #680370-100. This cross-references to a Dexter 10-36 seal which is the so-called "blue seal" which has a blue ring around the edge, a double flare, a spring in it and has metal on both sides.
Apparently, our 2015 23FB is a bit of an "odd duck" axle wise. It has 3000# rated axles with a mixture of light and heavy duty axle parts, 10" drums with 5 lug hubs. Unlike many modern Airstreams, my axles have the old-fashioned bearings that require periodic service.