There is an informative article in the December 2011 issue of
the Celator magazine called "Avoiding
Fake Oil Lamps."
According to the author, indications of authenticity are mineral deposits and root marks from long burial in the
ground. Indications of
fakes are the absence of a filling hole (which your
lamp does have), a
patina that washes off,
embedded hairs or brush bristles, glue and other materials that would have been destroyed during the firing of a
genuine
lamp. If your
lamp passes all these tests, you will
still need to take it to an expert to determine authenticity. Jim A
Add: there are numerous posts about
oil lamps on this board which might be helpful.