I'd say it was the Army's 5th Kavallerie regiment. They wore a metal Totenkopf derived from the design of the skull of the head-dress of the Imperial Prussian 1st & 2d Leib-Husaren Regiments; this metal skull was worn on the Nazi Army shoulder boards,(& of course they'd have the golden-yellow underlay like yours), & worn on the peakcaps, positioned on the front between the eagle & the wreath. In 1933, this skull began to be worn by the Regimental Staff & certain squadrons of the Heer's 5th Cavalry Regiment.
