Does anyone remember this little ditty from Reach?
Now look at Linda’s.
I don’t know about you guys but doesn’t her helmet look like a upgraded version of the GRD helmet?
it does.
As far as I know, she’s 100% custom, and the only similarity is the single extra scanner that Linda has like, a baker’s dozen of 
I personally feel that Recon is the base with heavy elements of GUNGNIR and CIO both incorporated and borrowed from… ie, Linda’s helm helped prototype many of the systems that went specific into the others.
Is her Helmet accessible through Req packs? Or is it commendation based?