[Rottler]

I have read your interesting interpretations which are not in agreement with the Petrick/Mankau book.

Your listed WNr. in the comparison of the variant C-2 during production and the variant C-4 from the loss lists are correct.
The following Bf 110 C-2 were listed in the Gen.Qu. loss lists as C-2 too:
2121, 3111, 3225, 3235, 3533, 3541, 3548.
Therefore it is not sure that your called C-2 were upgraded to the C-4 specification during the production. For example the Miag built aircraft 3533, 3541 and 3548 were lost as C-2 and not upgraded to C-4 standard, the 3532, 3534, 3536, 3545 and 3563 were built as C-2 and lost as C-4.
According to the Mankau/Petrick book page 176 many C-2 were afterward upgraded to C-4 standard, but not during the production.
Word for word: " Da .... in den Verlustmeldungen Maschinen als C-4 bezeichnet werden, die als C-2 gebaut wurden, sind Bf 110 C-2 nachträglich auf den Stand C-4 gebracht worden."

According to the C-Amts plan from 1 November 1940 FW were supposed to built 94 Bf 110 E-2. In the loss lists are about 73 allocated FW WNr. which appeared in the D-3 variant. Actually FW had delivered only 21 Bf 110 E-2, WNr. 4381-4400. Therefore the FW built WNr. 4356 was a Bf 110 D-3 (compare Mankau/Petrick pages 190, 324 and 325).

The variant "Bf 110 F" in the Gen.Qu. loss report is inexplicable.

I am no specialist for the Bf 110, I have only quoted the Petrick/Mankau book.

Regards
Leo