Hi Gizzy,
According to Wikipedia: As a special feature, the locomotive had been fitted with a two axle subframe supporting the brake frame for the electromagnetic rail brakes, which were supplied with current through the overhead catenary. Due to these subframes, the locomotive's wheel arrangement is correctly described as C′2′C′ in its original form, and B′2′B′ in its modified form. The two axle subframe, together with a small luggage compartment, has never been taken into account in the official classification of the locomotive. Strictly speaking, the locomotive should be classified as GDe 4/6 in its present configuration.
Hope this helps
Regards
MTheStrong