Cool find David !
You are right, I do have a similar pen in my collection. My pen is slightly earlier with the "short humped" clip with round ball end which was phased out in late1934.
This is a great thread. I firmly believe that there must be Autograph versions of all the Balance colours out there somewhere.

I haven't seen this one pictured in this thread. It is the only striated OS that I have seen.
Unless of course, anyone know's different.