It is hard to tell the cluster from the Milky Way. NGC6603 remains the small, mag. It receives another triple R, with magnitude 16 stars. Indeed the more northerly cluster lies only 39' away from the edge of the Lagoon's nebulosity. Dreyer's estimate that the cluster consisted of magnitude 20 stars is grossly overstated.
More recent estimates yield mag.
Dreyer describes it as pretty rich with little central condensation. Overall magnitude is 5.9, size is 13', stars estimated from mags. Both clusters shine through a rich, variegated Milky Way field. Dreyer describes NGC6522 as bright, fairly large, round, with considerable, gradual brightening toward the middle. Dreyer's estimate of magnitude 16 stars is a little extreme.