Agreed with John,
ebay is NOT a reliable reference. There is a very large number of misidentified stamp on
ebay. There is no vetting is it is simple to misidentify a stamp and ask silly prices, hoping that someone will take the bait. (It is called 'trolling for suckers'.)
The combined experience of the folks in this community is measured in centuries. Using the search function and spending an hour or two reading the previous threads is a good start.
Don