Here's what Floyd Tubbs had to say about
Stahlhelm shell production. He talks about the production ratios of helmet shell sizes 62; 64; 66 and 68...:
Shell size............Head size.............Percentage made:...............Percentage of 'Odd' size (estimate):
60......................50.5 - 52 cm..........................................................10%
62......................52.5 - 54.................10%.........................................40%
64......................54.6 - 56.................40%
66......................56.5 - 58.................40%
68......................58.5 - 60.................10%.........................................40%
70......................60.5 - 62................................................................10%
He doesn't mention sizes 60 and 70, but it might be reasonable to interpolate that these were grouped into the size 62 and 68 production with similar ratios if those four are taken as a total. So, if my math is correct (which it PROBABLY IS NOT), this would mean that the largest and smallest sizes made up 1% of total production.
At any rate, it may be reasonable to expect that these numbers were based on similar numbers from Pickelhaube production.
Any thoughts?
Ron