Dear Violeta,

Thank you for your request. The presented object is an oil or petroleum student lamp made by Charles F. Spencer in the late 19th century. The lamp is made out of brass, glass shades and steel clips to fix the shades. Charles F. Spencer was an inventor who applied for many patents in the last third of the 19th century. His inventions range from technical products like this lamps, glass products like a self-sealing fruit jar or buttons. One one side this lamp is a very interesting technical document of a period, but on the other hand, it is a mass-produced article of daily use. It was probably made by the Manhattan Brass company. Sadly this lamp is not in the best condition. Nevertheless, it is a searched object on the market and a collector would invest some money in a refurbishment.
An estimation would be between 150 to 300 USD.
This estimation is based on actual recent past recorded auction sales of comparables. Retail "asking prices" can be higher and vary.

With best regards,
Georg