I have browsed some regaring the "Lolland-Falsters Bøssemagerværksted" and nothing really pops up. However that does not mean that it have not exsisted. I will do some asking around. Sometimes back in early days one could run a business without calling himself something specific in VAT registre.
That rifle could have been put together after WW2 with many parts by a good talented mashinist or toolmaker running a different business than "guns".

Intersting it is. More pictures would help ofcouse.