A true DD is produced during a hubbing stage where the working die is produced. Before the single squeeze process of hubbing occurred, it took 2 or more squeezes to produce good enough images for pressing the final coin. Between these steps the 2 dies would undergo heat annealing to soften the metal for the second squeeze. To do this , it was removed from the machinery and heat treated and carefully returned in 'same' orientation. And most were. Sometimes due to several different reasons, the orientation would be different from the first squeeze, and when a coin was struck with the doubled die , it would show both~ doubled die coin.... Now if this particular DD die was put into misadjusted press, that had been well used over time, tolerances were not original and vibration, slipping, etc. could occur, Thus since it was not the action of hitting the coin, but as the die arose from the coin after the strike, it was called strike doubling or mechanical doubling and Post mint Doubling or Machine Doubilng effect.............. The chance of just a DD were slim, but the chance of the DD with MDD was much slimmer, and few combinations of such occur. I have never heard of one, but in theory , .....if such die/machine was overused, the die could theoretically develop deterioration damage also for a trifecta IMO. Jim
I'm done. I tried my best. Send it out and get back to us. I would like no better then to be provin wrong. Good luck
Thanks, all one can do is try. Actually images have to be sharp, far more important than being big. Jim
Thank you, I sleep well at night! After decades of teaching a dog-eat-dog professional college program, decisions stopped bothering me once made. Jim