Hi 'Nando,
with the patination looking 19th C and the lack of wear inside the fork, a musket rest seems unlikely. The shape does give it the 'right' look but I believe that the rests were used for the heavier, earlier matchlocks....so would be older than the 19thC. A finial perhaps, flag pole? or maybe worse ...a curtain pole finial ...
With such an imagination....the seller should do listings on eBay
Some pictures of musket rests.....
Best
David