[Merlin]

The main production versions of the He 51 were indeed the He 51A (207 aircraft) and B (300 aircraft) followed by some 105 He 51C - as published in Prien, Stemmer and others book JFV der Deutschen Luftwaffe 1934-45, Teil I. That table was created by means of test pilots Flugbuchs from Heinkel, delivery data for individual aircraft and loss data - even those from the pre war time. The production at Heinkel and the licence companies ran from February 1935 until spring 1937.

During repairs or heavy maintenance stops all early aircraft were upgraded to the C-version which could be identified by an external tank. This upgrade is visible in the first column of each of the three pages pages presented by Seaplanes. The version is given always as: Abwandlungsmuster (modified version). During this modification process the remaining eyamples of the 30 former seaplanes He 51A-2 and B-2 became He 51D without floats. All He 51D were lost later with land based training units.

The He 51 has had a limited career as a fighter within the Luftwaffe, after roughly two years in service most of the groups became re-equipped with the Bf 109 or D during 1937. Those units, which were equipped with the Arado Ar 68, became re-equipped in 1938.

The He 51C “white 5” from the photo belonged to 1./StG 165 at Kitzingen. The initial equipment of this group since it’s formation in March 1936 were He 51 and Ar 65 with tactical markings like a fighter unit but without any colour code at the engine. These aircraft were replaced by Hs 123 in spring 1937.

Several aircraft of 1./StG 165 have had an individual symbol on a white square with a black border. Known examples are:
“white 1” a red devils head
“white 5” a winged dragon or similar
“white 10” a horse head (not a sea horse)