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Maybe Limnophora triangula.
Manual of Central European Muscidae gives "Frons as broad as 1/3 of head width in both sexes, 2 orbitals on each side, fronto-orbital plates brownish grey, parafacialia silvery white, brown frontal triangle often reacdhing anterior frontal margin, ...Scutum with 3 longitudinal stripes, 3 post-sutural dorsocentrals, presutural acrostichals in 3-4 irregular rows. .. Eurasian, in Europe from Spain, Corsica and Sicily to Scotland and Lapland."
It looks a bit 'clean' compared to the other photos of the species on this site but your specimen might be just newly hatched (or it could be the flat illumination).