ACtually, I know of 88 6.5" Pre war HDs shipped and 118 4" HDs shipped, not what is still in the population, so I would say that both of these barrel lengths are pretty rare and to find one that is as new as it left the factory is extremely rare.
Actually, the 6.5 " Pre War HD is the most rare Pre War as it was not cataloged and a special order. The 5" was the main barrel length, but I feel like the 4" was really coming on in 1939-40 and that is why in my opinion it was the most popular barrel length for HDs after the war. My pre war...
As our leather expert and moderator knows, I have been looking for a S D Myers holster that would fit a Heavy Duty. Well a few weeks ago I was looking at the for sale ads and saw a 4" N Frame basketweave holster for sale. It took about 5 seconds for me to type "I'll take it!". When it arrived...