On October 2, 1990, just one day before reunification, the now 67-year-old inventor's rotary screw cooling compressor was approved by East German patent officials and given the number DD 298536.
“It was pure coincidence, I was surprised myself that I was the last one,” said Mosemann.
After 20 years, the lifespan of a German patent, his idea's protection expires at the end of October.
As the development director at the state-owned firm VEB Kühlautomat, Mosemann was one of the most productive inventors in communist East Germany, known as the German Democratic Republic (GDR).
With his team, Mosemann created cooling systems still used around the world for everything from supermarket freezers and airplane climate control, to extremes applications such as chilling indoor ski-slopes in Abu Dhabi.
One in every five GDR patents came from VEB Kühlautomat, and of these 71 were in Mosemann's name.
In contrast with capitalist West Germany, GDR patents were available for use by all of the country's socialist firms, and while inventors received a premium, they could not benefit from any profits garnered due to their creation, according to Leipzig historian Matthias Wießner.
“They could be used by all of the state businesses,” he said.
But inventors such as Mosemann were at least honoured by state officials – he received a medal for his innovations on the country's national day in 1977.
Profiled by Zeit Wissen magazine earlier this year, he said he was motivated by a love of invention and not money, finding the later adjustment to capitalism a challenge because he “didn't know how to sell things.”
Indeed, dire economic conditions and goods shortages in East Germany spawned the creation of some unusual products. Scientists created a replacement for unavailable citrus fruits made from a mixture of pumpkin, green tomato and candied orange peel.
And one patent, issued in 1984, was designed to “improve the raw materials” of beetroot by “pepping” them up with a chemical pineapple flavouring in order to fake the taste of tropical fruit.
While some of the more bizarre inventions ceased to be of any use following German reunification in 1990 as the east was flooded with imported Western goods, some had already been copied by their counterparts abroad.
Under communist rule, the Mosemann's company had no money for patent fees in places like the United States, where their inventions were simply copied right away.
“Then when we wanted to enter the US market, we were stopped,” he said. “We had to first explain to the Americans that they were using our inventions and not the other way around.”
After reunification VEB Kühlautomat was acquired by food and energy system provider GEA Group, from which Mosemann has since registered about 80 new patents.
“The last one was three or four weeks ago,” he said.
In addition to his cooling compressor, a handful of GDR patents found lasting success overseas following reunification. One, from company Carl Zeiss Jena, created the fibre optics which project the stars onto the roofs of planetariums the world over, the patent for which expired in 2006.
Meanwhile other military-related patents used for manufacture of explosives and weaponry remained state secrets, according to historian Wießner.
In spite of the benefits of reunification, Mosemann admited that he sometimes misses his time at as an inventor in former East Germany.
“Before engineers were paid less, but there was more room to be creative.” he said. “Nowadays this kind of freedom is a little hard to come by.”