Are you sure of the name and the spelling thereof?
Neither Pete Mikalajunas' list nor littlegun include Lachausse/Lachaussée as a gunmaker
http://www.littlegun.be/arme%20belge/a%20a%20artisans%20identifies%20gb.htm#L Pete has NL as N. Lajot & Cie and NL in an oval as N. Lasot & Cie
Scroll down here about 1/3 for the Lajot logo on an action flat. Lajot is a 20th century maker.
http://www.littlegun.be/arme%20belg.../a%20lajot%20nicolas%20et%20cie%20gb.htm Steve Nash's encyclopedic thread includes a reference to a 'NL' mark
https://www.doublegunshop.com/forum...p;Board=1&main=45609&type=thread I found a statement that Lachausee did not become New Lachausee until the 1992
https://ufa-belgium.com/wp-content/uploads/2021/04/1610329_UFA_FICHES8.pdf
