I have to say it looks exactly the same as the D5500 wall brace. Then, when I look at the B&H, Adorama and OmegaSatter web sites the D5 brace looks like what I got! As you well know the D5500 column takes bolts vertically at the top of the column. This D5 brace is the same, (has holes for vertically "dropping" bolts,) but I see nowhere for them to go. Now it did come with a replacement "L" plate to which the counterbalance springs attach. If I reverse that bracket there are two small screw holes if I added some washers - but, compared to the bolts used on the D5500 they're tiny, and I'm not sure of much use. I guess they'd be sufficient to stabilize the column and it's not like they have to take any great strain. Just seems that two small screws in a solid wall brace like that is nuts.
I haven't got to the D5500 head yet. But I have a list of the links to your threads on it and I'll be all over them! I could well become a pain in your ##s !!!
Bob H