Gents,
an interesting puzzle, let me give it a shot.
To start, I think there is a lot of confusion, misquoting and wrongly copying in all this.
A few facts (I think):
- There are pictures of Stukas in the French campaign carrying the S1 code and the I./StG76 emblem (I have at leadt two of them)
- F1 was during the entire French campaign the code of Do17Z's of KG76
- III./StG77 carried the F1 code + II. Gruppe letters after July 1940
- There were apparently losses of Stukas coded F1 + II.Gruppe letters during the French campaign (see Rosch)
Furthermore Rosch Luftwaffe Codings and Markings gives the codes of I./StG3 (formed 7-1940) as formally S7 but with a lot of S1 used too.
My interpretation is therefore the following:
- I.StG76 used S1 as mentioned by Peter Cornwell and confirmed by losses and pictures. It used the standard I.Gruppe Staffel letters B,H,K,L.
- This group was renamed into I./StG3 in July 1940, where the old aircraft continued to use their S1 code until written off. There are further sources confirming that Hptm Sigel of I./StG76 took his crews and took command of I./StG3. All/most new aircraft got the regular S7 code. All S1+ losses mentioned in Rosch carry indeed only I.Gruppe Staffel letters, consistent with point 1. above
- The F1 code belonged to KG76 during the French campaign. However, halfway the campaign the II. Gruppe was withdrawn and started to convert from Do17Z to another type, probably the Ju87. This is confirmed by the Ju87 Osprey book of John Weal, although he erroneously talks about the I. Gruppe. All Stuka losses in Rosch only use II. Gruppe codings (C,M,N,P). This withdrawal of the II. Gruppe is also made plausible by the loss list in Rosch, which shows a clear gap of II. Gruppe losses during the time it used Do-17Z. [Rosch, by the way, makes his story very complicated by trying to explain how at the same time I./StG76 and II./KG76 were using the F1 code. I think for once Rosch is wrong here.]
- What is not clear to me is whether this reformed II.(St)/KG76 has operated its Stukas before July 1940 as suggested by the losses in Rosch of Stukas coded F1. This would imply an unusually fast conversion of the crews from heavy bombers to dive bombers. I can only explain such a scenario if fresh crews that had been training on the Stuka took the II.(St)/KG76 unit code while the II./KG76 crew started conversion to probably the Ju88.
- By July 1940 the II.(St)/KG76 unit became III./StG77, taking the F1 code with them, still only using the Staffelletters C,M,N,P of the original II. Gruppe.
- The use of 5M by Stukas is not confirmed by any source I have, so I would simpy discard that as an error.
Well, so far my theory.
Hope others can confirm or correct.
Pieter