My gut reaction is "planchet flaw which separated from the coin later during circulation." If it's a hit, metal had to go somewhere. We see nothing of that in this image, and I guess you'd have mentioned it if metal was obviously displaced towards the obverse. The curve of the rim seems uninterrupted. Had it been a void during the strike, it would certainly have affected the strike quality in that area, and we don't see any of that. The denticles are as-struck in normal configuration. So the most sensible explanation to me is a detached lamination and a little circulation rounding the sharp edges afterward. Let's see what others think.
Plantched damage/lamination. Looks as a piece of the planchet flaked away during production and the sharp edges have worn down through time.
It's difficult to say from this one photo. I lean towards lamination and it looks like a small crack has formed just above the T in the missing metal. However, as you well know, Gold in very small amounts was cut away from coins by dishonest people. Gold is a soft metal. The top edge in towards the coin above E and the outside lower edge above A are jagged but in between them is a fairly straight line, like from a cut. It's definitely worn smooth. Take a closer look at this and let us know what you think.
This is another valid potential explanation. I should think a deliberate removal would exhibit a smoother overall appearance - the normal practice was to shave the edges (now you know why coins are reeded) - but it belongs in the differential.
I might eventually send this coin in (after I get enough to make it worth while). It is XF/AU details cleaned, but if it grades as an error it might be worth it. The last time I thought I had a planchet flaw they ended up grading it as damaged.
