Don,
While all #2 nibs may look alike to some people who are not real familiar with them, they can be told apart without writing. But of course writing will be the ultimate test.
if you go here
Wahl Nibsand scroll down to my post (its the second one) you will see the basic variety of # 2 nibs that Wahl made available. If you look cloesely, you will see that while none of the #2 nibs are marked for their characteristics, that they have subtle differences in their shapes. As a rule, the longer the #2 nib and the narrow taper toward the tip are the flexibiles and the ones with the faster/shorter taper to the tip are the less flexible. Of course there were many of these that were made for special purposes other than to be flexible for not. Maybe that will help you and others to try to select what should be a flexible nib from photos or on ebay. Also if you are corresponding with a seller, try to get them to photograph the nib from the side so you can also see the thickness of the nib and if it shows areas where it is reinforced for stiffness. (the Maniford nibs (very stiff) were like that.
Hope this helps
Syd the Wahlnut
PS the text at the post mentioned is pretty good reading to get a feel for the Wahl attitude about their nibs.