When did Germany drop the spike helmet?  I see Hindenburg wearing shortly before he died in photo.  As far as I can tell, it seems to have disappeared from German uniforms after WWI, but I really don't know. I don't recall ever seeing a WWII picture where a German was wearing the spike helmet.   

The Pickelhaube stopped being issued when the war was still ongoing, like 1918, maybe even earlier in 1917. It still was worn by those who still had them when on leave and what not back in Germany however. With Hindenburg and any other high ranking generals, maybe even colonels, wearing it still in the 1920s was simply a tradition thing, it had nothing to do with it being a Reichewehr issue item

Thank you for that!  That makes sense.  The spiked helmut had a good run, but not ideal for combat.  Hindenburg looks good in though!