The plot thickens!
There were also 2207B, 2207D and 2207D variants:
The 2207D was the 2207C when fitted with a muting circuit.
As the bandspread facility covering six marine HF bands was a “normally fitted” facility, it would appear that it was what might be called a “delete option”. That being so, perhaps the 2207E was a 2207C without the marine HF bandspread? In which case the 2207F might have been a 2207E with the added muting facility.
The above attachments are from a 2207C document dated 1967 November, so quite late in the Atalanta production run.
Cheers,