Two separate scientists filed patents in the US the same year
for different types of the same instrument.
French scientist Bernard Epzstein first demonstrated his M-Type
BWO 1951. Meanwhile, Rudolf Kompfner introduced his own,
independently-conceived O-Type BWO around the same time. Both filed
their applications in the US in 1952. (Epzstein was granted patents
in France, UK, and the US for his BWO)
Epzstein's patent was filed a month before Kompfner's in the US,
but most reference material points to Kompfner as the primary
inventor, supporting this with the large body of research and work
he had done in the field prior to filing this official
application.