That looks like the early 51 and 50 fat boy cable. The metal support is called the "toeboard Gusset".
Here's what I wrote on the 503 about this:
The very early cable assembly was a Titeflex unit PNB37559 (WO PN 801191 & ORD PN 776732).
The later cable assembly was a Titeflex unit PN B36834 (ORD PN 7539500) .
None of the parts books specify when the switch took place but odds are it was shortly after August 1951.
The only difference I have noticed is the shielded sleeve asembly composition and diameter. Both have straight ends on each end. My 1952 unit 24.5" tip of connector to tip of connector. The rubber coated shield sleeve has "Titeflex Type 159A" on it.
Both have ORD stock number prefixes of G742 (REO 2 1/2T 6x6).
My late 52 cable.
This is what I believe to be the correct early cable assembly.