There are so many variations from country to country it's hard to judge. You have the Le Mineur knives (french soddies) and the Navaja style soddies. The sodbuster really is the most basic knife. I've recently seen three blade sodbusters (oh the blasphemy!). Traditionally they don't have bolsters, but I've seen custom jobs with them, and even modified factory soddies with bolsters added, as well as a liner lock and pocket clip. Traditionally speaking, those options disqualify it from being a soddie. I say if it looks like a soddie it's a soddie.

I think just as beauty is in the eye of the beholder, a soddie is in the eye of the beholder.  I say if you are collecting soddies, collect the ones you think are soddies.