Where's the Type VIIB?
 

I am in the initial campaign and had been using the Type VIIA for a few months. Upon returning to port on one of my last missions, I was offered a new boat. I assumed it was going to be a Type VIIB since it was Nov. 1939, but it was a Type VIIC...

Any ideas where/how I get a Type VIIB (it's my favorite sub)?

Were there even Type VIIC's in 1939?

Thanks!