Great helmet. As Ruski says don't clean, mess, strip, alter, apply anything!!!! The style of decal (silver eagle) determines that it's Army. Gold eagle would be Navy. White flying eagle is Luftwaffe.All the organizations had there own insignia. If the leather was still present and in good condition the helmet would be around $1500, anytime something is missing whether age or well meaning individual, the item looses value. This is because unaltered and excellent items are harder to find and worth a preium to most collectors. Moral of the story "It is what it is so don't play with it". If you get rid of it, you'll be sorry later on.
There are 3 basic combat helmets M35, has pressed in air vent with rolled rim.
M40 has stamped air vent and rolled rim (which is what you have).
M42 has stamped air vent with flaired out rim.
RLB is Reichsluftschutzbund or Air raid Protection.
