Got this unidentified for a modest price, thinking it was a colonial Spanish coin. I was having trouble finding a match, but now I think it's probably a Seville mint 2 reales, Felipe V, 1737, like this one on Numista. It should be 27 mm dia, but mine is a little over 25 mm, making me wonder if it is a fake. Comparing to the one below (not mine), it looks as the design is clipped around the edges in a consistent way, too much for just wear and tear. The top of the crown is cut off, and the letter tops touch the edge instead of having a strong border. Could this be authentic, but shaved around the edges to make a clipped coin?
Not an expert, but it looks real to me too. I actually prefer coins like yours - lots of signs of use. Spanish 2 reales of this era were used a lot - because they were of lower silver purity than the 2 reales coming from Spanish Colonial mints (Mexico, Peru, etc.), they circulated heavily. They were counterfeited too - I recently picked up a worn pistareen from my local dealer's junk box. When I went to research it, I found it had to be a fake - 1761 dated coins should have had Carolus III, not Philip! In a way this makes it more interesting - it is a fake, but it is an old fake that saw a lot of use. Here's Numista on a genuine 1761 pistareen: https://en.numista.com/catalogue/pieces17955.html Here is a good article on pistareens being used in the North American colonies. Lots of history with these: http://numismatics.org/wikiuploads/CNL/Pistareens.pdf
What does the edge look like? It could not shrink that much in diameter just from circulation. If it was genuine but shaved, then a specific gravity test should still show a 90% silver coin.
@jgenn: Sorry for the delay--I had to find it again and take it out of the packaging. Weight is 4.55 g, should be 6.77 g for a Seville 2 Reales. Diameter is just over 25 mm. Should be 27 mm. Edge is pretty smooth. I think it's clipped, because for other coins I've seen with a lot of wear, the face details should be worn off much more, especially near the edges. Instead, most of the center detail is still visible, but the outermost portion of the design is just gone. If you compare to the one on Numista (bottom image), the letter "A" in the 6:00 position touches the edge, while on an intact one there should be a 1 mm border.
Found a Chile 2 reales from 1812 for size comparison. Both the 1737 Seville and 1812 Chile ones should be about 27.5 mm, 6.77 g I definitely think 2 mm of the perimeter of the Seville coin have been clipped off. Seville 2 reales is 4.6g, 25 mm Chile 2 reales is 6.1 g, 27.5 mm Looks like the coin clipper took advantage of the fairly wide design on the edge and shaved off just enough that all the text would still be visible. You can barely tell that the top of the crown on the reverse is clipped away. Kind of cool as a historical artifact, even if it reduces the numismatic value of the coin.
It also appears to be thinner. Until you determine how much silver it contains, I suggest you not consider it to be genuine.