Research showed it could be a tap but the threads in the curved decorative drop spout have me puzzled. Could it be a lamp valve or something with machinery?
Nokta FoRs Gold, a Gold Cube, 2 Keene Sluices and Lord only knows how many pans....not to mention a load of other gear my wife still doesn't know about!
That looks like a grease / oil cup from a piece of machinery. It would be oriented vertically and the smaller hole would have a flapper door that would close to keep it covered so no debree gets in.