I suspect that the lamp was never an oil lamp but always electrical....with hints at old oil burner. But that "burner" on top sure does look real.
I see no way that could could have originally been an oil lamp...and mercury glass is very fragile and will turn dark if the seal is broken...it consists or 2 layers of glass, with mercury in between and sealed, usually with wax.
The light sockets with the pull chains are not new, but frankly I don't see how this could have been a lamp? Where would the shade fasten? Have you tried to unscrew the electric part?
Something looks fishy....where did you get it?
Linda C

The item sitting on the top globe is designed as a kerosene burner. There are air vent holds on the under side of the metal holder and the pronged top of the holder is a typical design for holding a glass chimney. Its too bad it has been ruined. The wick elevator has been removed and a hole drilled in the bottom for the electrical wire.

However, there is are suspicious elements. Normally, the glass container for the kerosene was transparent enough to reveal the liquid level. This was necessary feature so that the owner knew when to refill. Also, the height to width ratio is suspect. A desireable keresone lamp has a wider base to stableize the lamp and guard againt tipping it over, a greatly feared hazard with kerosene lamps.

Thanks for the information!

Any ideas on value in current condition?

I think the very top unscrews for a shade with a" metal washer" type thing that sits right on bolt & screws down, it was never an oil lamp. The bottom is similar to couple of mine.That piece on bottom is metal, I've seen where people have bent them trying to get them off, doesn't come off. You replace cord by loosening that piece around cord & pull it out the bottom after you have taken it apart from the top, then you slid new cord up the lamp & attach to 2 top pieces & you are all set but I haven't replaced this 1 with 2 lights so cord must be split & have 4 wires in it instead of 2. As Linda said mercury glass wouldn't work for that. Does that lacey piece right under the bell chains have a little flat piece coming out of it on the other side that we can't see, if it does it may have printing on it by company that made it. Does it work? With right shade would be very nice lamp.