Dyptic Oils on wood signed HL with the monogram on bottom left part of the St Joseph. The monogram is not rare on small sized paintings as on the 1850 portrait of Mr Nollet  Oil on wood 13,5x9,5cm sold at Im Kinsky
Kunst Auktionen Vienna 5-12-2011 lot 144.  There was a "Holy family" in the January 1883 Exhibition of artworks by Henri Lehmann at the École nationale des beaux-arts in Paris, under n°103 in drawings category page 23.
He was a great decorator, subtle portrait painter and leading designer, Henri Lehmann was one of the most unknown painters of the 19th century. A pupil of Ingres, he suffered from the ostracism that struck the
innumerable artists from this workshop, with the possible exception of Chassériau, which he approaches in many ways. Detailed study in preparation. I welcome serious offers.