"Handcrafted" Hardy Reels
The question you asked is one that probably doesn't have and exact answer.
When Hardy began making making their own reels (their earliest reels were supplied by others) in the late 19th century the major components were cast and then finished 'by hand'. But, 'by hand' always involved machine work. Visualize the holes in the face of an old Perfect - they were drilled by a machine operated by someone. Over the years, Hardy used more and more machines to keep its costs down. Also, the casting process would have became more sophisticated as time went on, reducing the amount of work needed to finish a reel.
The complete elimination of the use of castings probably could not have been accomplished until CNC machines were used in the Hardy reel shop, sometime well after World War II. But, by then, I expect that the majority of finish work had already been taken over by more and more capable machines.
Another way to state your question might be this: When did Hardy reels transition form the "classics" of the earlier 20th century to the "modern" reels of the late 20th century? I've always considered the years around World War II to be that time.