OMC I found this again after reading it a while ago. I copied from wiki but I found it on numerous other gem sites that I don't want to quote from
The Asscher Cut
In 1902 Joseph Asscher upheld his father’s reputation for skill and innovation by designing the original Asscher cut. This emblematic cut was the first signature cut to be patented. The Asscher Diamond Company held its exclusive patent until the Second World War and saw strong sales internationally.
World War II
During the Second World War the Nazis entered the Asscher Diamond Company’s Amsterdam headquarters and seized its diamonds. The Asscher family's members are Jewish, and were thus subsequently deported from the Netherlands and interned in concentration camps, along with nearly all of the company’s polishers. During the war the patent on the original Asscher cut expired. With no one to renew the patent, other companies started to utilize the Asscher cut, leading to market confusion about the origin of many Asscher cut diamonds. Some companies chose to call their Asscher cut diamonds square-emerald cuts instead. Many of these diamonds were cut for yield and did not necessarily follow Joseph Asscher’s original proportion calculations for the Asscher cut, which specified parameters for the diamond’s crown height, table size, and facet alignment.
 After the war
In 1945 the war ended; only ten Asscher family members and fifteen of the five hundred polishers survived the Holocaust. There was no company to return to: although Amsterdam was once the world’s diamond polishing capital, the diamond industry there was wiped out. This was due in part to the liberation of Antwerp, which came to emerge as a major diamond polishing center.
In 1946 Joop and Louis Asscher were invited to utilize their expertise and start a new company in New York. However, they chose to remain in their home of Amsterdam and to rebuild the Asscher Diamond Company.
I am not sure if/how patents differ from group to group. My dad has held many in the engineering world. He might have some insight into it.