It's a forgery, if you bought it from eBay
it is a forgery, if you bought it outside of eBay
it is a forgery. An inverted frame error (the swan is in the correct position) was sold from the late Arthur Gray collection in 2015 for $250,000.
The authentic 1854 specimen (printed August 1, 1854) is on the left and is from the Duke of Leinster Collection at the National Museum of Ireland. The font is very clear even with one as ratty as this one. The stamp on the right is your specimen, the font is blotchy, the blue is of an incorrect shade and the stamp is printed on modern paper; it may be a 1970s Smits reprint.
Does your stamp have a watermark?
These stamps are never sold cheaply.