Model 1867 Oldenberg Infantry Regt 91
 
Model 1867 Oldenberg Infantry Mannschaften (Other Ranks) Pickelhaube for Oldenburgisches Inf. - Regt. Nr.91 Oldenburg X.Armee-Korps. Unit marked with a branded OIR 91 on the rear visor.

There were several significant changes made to the M1867 helmets from the M1860 pattern. These included a round spike base and front visor, removal of the rear spine, and a new system for securing the front plate. Please refer to "Spiked Helmet Evolution" on the main index page for details.
 
 
A view of the M1867 Wappen (front plate) for Oldenburg. Note that for Oldenburg, a regular Preußen bandeau " MIT GOTT FÜR KOENIG UND VATERLAND" was used, superimposed with the Oldenburg Wappen (crest). The M1867 Wappen was secured to the helmet shell with two flat sliders that replaced the threaded bolts. The plate fit into corresponding two female slots secured to the front of the helmet.
 
The liner of the M1867 remained the same, but the threaded bolts for securing the spike base have now been replaced with split brads bent back against the inside of the helmet.
A side view showing the high dome of the helmet.
The helmet is unit stamped OIR 91 on the rear visor.
 
A view of the rear showing that like a typical M1867 helmet, there is no rear spine as per the M1867 regulations.