When one reads about how difficult the Kaiser was with other badges.... and the small amount that were approved, mainly just for the duration of the war.... I must admit I am veeery spectical, to the point of disbelief, that the FW wore a skull on their Pickalhaube... You can pin a badge on a cloth hat, or collar... but the Spiked helmet is strongly rooted in Tradition, pomp and ceremony... a whole dirrent league of uniform item to mess with... That there are helmets floating around with skulls on, there is no doubt, but I would be curious to know how and when the skully made it onto them...
I have never ever seen any period references to the Minenwerfer having any skull connection?