Element 43 was named masurium (after Masuria in Eastern Prussia). The group bombarded columbite with a beam of electrons and deduced element 43 was present by examining X-ray diffraction spectrograms. The wavelength of the X-rays produced is related to the atomic number by a formula derived by Henry Moseley.  The team claimed to detect a faint X-ray signal at a wavelength produced by element 43.  Contemporary experimenters could not replicate the discovery, and in fact it was dismissed as an error for many years.
It was not until 1998 that this dismissal began to be questioned.  John T. Armstrong of the National Institute of Standards and Technology ran computer simulations of the experiments and obtained results very close to those reported by the 1925 team; the claim was further supported by work published by David Curtis of the Los Alamos National Laboratory measuring the (tiny) natural occurrence of technetium.  Debate still exists as to whether the 1925 team actually did discover element 43.