I have a problem with a "fireman conversion" description for this helmet and we will get to that. For younger collectors....many war surplus hauben were converted to fireman helmets after the war, old wappen holes were plugged and new finish was applied to cover up the old holes on the outside. They also had new liners installed if needed. In the majority of cases a city or district wappen was put on the front of the helme along with a metal "comb" in either white metal or brass along the top of the helme. I will post a pic of one of these tomorrow, in the meantime think raupen helme. The idea was that the fire helme needed to provide metal protection from overhead falling debris, so thus, the comb on the top of the helmet. In order to install this comb, extra holes had to be punched into the haube shell along the back, top and front of the helmet and that is a "tell" whenever we collectors encounter a helme that has been reconverted from fire to pickelhaube. The other significant revelation, is the depression lines in the shell/finish caused by the metal comb being put on the war surplus haube. These are always very clear and hard for any "faker" to hide. So, this brings us to the ebay example in question and my initial comment in this post...I do not see any comb lines in the top of the helmet, no indentations, no evidence of a "comb" being installed. In this example, in my opinion, I think that what we have is a pre 1915 cruciform based haube converted to an M15 with grey metal fittings. We see original M15 wappen, partial visor trim and rear spine. On top, a post war, home made spike, perhaps made for theatrical purposes?? Either way, the asking bid price is ridiculous and obviously made by a seller, who has no knowledge about real pickelhauben.
As promised, pics of the fireman "comb" fitting"
The split brad at the tail of the fitting requires a new hole to be punched in the surplus haube as does the front screw post. The middle post usually uses the original back hole of the original spike base brad. As mentioned, the weight of this fitting and the fact that it is clamped down on to the shell causes depressions in the shell and marks in the finish. These issues make it hard for a faker or even an honest collector to reconvert the war surplus haube back to it's original condition, plus, you have 2 extra holes punched into the shell which were never there when it was manufactured.
Ron
:x #-o #-o #-o :ANGRY: Ha ha, not really 
