From the Back it looks 110% English to me.
My Theory? Well since it is believed for the most part that Vuillaume farmed out the Bass work and the fact that JF Lott Jnr. was his good friend I would say that this one was made in London and possibly by Lott Jnr or Snr. If 1860, Jnr. If 1850, either as the father died in 1853, Jnr. in 1871. Lott Snr. was famed for his DB's even in his own time in London.