The 251/6 command and 251/3 radio-vehicles are hard to tell apart. Initially the /3 was "renumbered". From the first days of the war this vehicle is issued to division-commanders and higher ranking officers (often equipped with Enigma coding-decoding device). Later in the war when more vehicles come available they are used more extensively to control formations and for liaison with tank-formations. The early vehicles are relatively rare, but photographed very often. The differences in equipment are enormous. The biggest difference between 251/3 and 251/6 is the office like function of the 251/6 with various decoding and deciphering apparatus. Many radio configurations are seen. Distinguishing is best done by the antenna. Generally speaking the frame-aerial is the one in the beginning of the war. Being to conspicuous it disappears structurally in 1942 in favor of the star aerial and the 8 meter rod-type. Frame antenna's are seen on A,B and C versions. Several front modifications are known. One photograph even shows an antenna from an SdKfz 232 (8 rad). D versions and some C versions are seen with a star antenna. Often a scissors binocular is seen. Late in the war infra-red equipment is reported on the 251/6. This could easily be the 251/18. A field modification often mistaken for the 251/18 is a large platform above the drivers compartment serving as a map table. This is seen on A and B versions only. Since the numbering consisted of up to number 251/12 in 1942 a 251/18 cannot be on a /A body. The frame-version is still seen in 1944. Most D's have the star antenna. Many field-manufactured versions are photographed. Luftwaffe unit's sometimes use the 10 meter "Flivo" pole-antenna. There is a picture of a 251/6 with a S Pzb 41. Some sources separate 5, some 9, versions of radio-equipment.

Radio configurations that have been described in various documents include:
FuG11 - FuG Tr. (Before 1943)
FuG11 - FuG12 - Kdo.Fu.Tr. with 9 meter pole antenna and frame.
FuG12 - FuG19
Fu.Tr.100Mw(gp)
Fu.Tr.80Mw(gp)
Fu.Tr.30Mw(gp)
Fu.Tr.15Kzw(gp)
Renumbered 251/3s would have one of several radio configurations:
251/3.1 carrying FU-8 and FU-4
251/3.2 carrying FU-8 and FU-5, the tank formation radio.
251/3.3 carrying FU-7 and FU-1, for air-ground co-ordination
251/3.4 carrying FU11, FU1 and FU12, command version
251/3.5 carrying FU11, and FU1, command version
Given the number of different radio and antenna configurations, as well as the number of one-off conversions done in the field (including 'home-made' frame and spar antennae), we could argue for years over which specific version the vehicle is, and without being able to ask one of the people in the picture we'll likely never be sure.