On my data plate it says that the D.S.O. is 17, but every source I've looked at skips numbers 16-20. What's going on?

 

My handy decoder book says that DSO 17 is Washington. The only other one it lists between 16 and 20 is 16 which is Philly. I'm not sure what your sources are but they do not sound like they are very complete.

 

Guess I haven't used my handy decoder book in awhile becase that DSO I just looked up is for a 67 not for a 66. So you are right there is nothing listed for 16-20 DSO. I would bet that the Washington DSO for 67 is correct though.