I would try the what is it forum if you haven't already posted it there. You can ask for help with cleaning and probably get an ID on the date of the lock.
nice find. i have a similar find--a light electrolysis will take off surface rust--don't over due it. i once dry--i sprayed clp (clean, lub, protect)--a gun care product. let that dry--the satin spray laquer.
google 1800's padlocks images--you may find a similar piece. marking on dust shield may point to manufature. mine is english--around 1850.