505nm will have a lot more blue in it but will still be an obvious shade of green. 520 nm looks like a pure green or traffic light green for some.
Edit: I’ve taken pictures of 520nm before on cameras and they don’t usually struggle to depict that shade of green so I’m definitely leaning towards close to 505nm. Tip for you, I find this with my 520 and 493nm. Sometimes intense bright spots knock your colour perception off slightly, but instead shine it at a corner and look at the illumination it causes. This is how I see the difference between 520 and 532nm more easily. Also my 493 will look greener under spot conditions yet way more cyan when illuminating an object. Our eyes are not perfect spectrometers. Another neat trick is when you observe different wavelengths. I can make my 493 look light blue with no green if I observe a higher wavelength laser ( green, yellow red etc) for a period of time. And then switch to 493, also works in reverse too with shorter wavelengths.