[John Vasco]

Stig,
As you probably know from the Petrick/Mankau book, the 'C-3' is still something of an enigma.

If it is simply an upgrade of the aircraft from MG-FF to MG-FF/M, then no external difference can be seen.

If the information that Peter holds is documentary/photographic evidence, then it introduces another intriguing matter into the whole issue of production run W. Nr. I would say at this point that if Peter offers the W. Nr. 1863, and the sub-variant as a 'C-3', then I'm pretty sure that he has the supporting evidence in the first place.

Most fascinating, and the kind of scenario that keeps us pegging away continually at this research thing!