I think the 10- prefix indicates it was made by another manufacturer (either under sub-contract or under license), possibly identical to the HS 6229A design, or to a modification (-18?) that was approved by HS as a replacement for the normal HS blade.
I have seen prefixes like the 10- before but have not been able to find the relationship to the sub-contractor or licensed manufacturer. The 10- might indicate Nash-Kelvinator.
Or I could be totally wrong.