Quick hint
Leave this puzzle until after the Red Tower. The two four-digit values describe a place, not a code to type into the nearby structure.
Stronger hint
Unlock the Map Room and take the foldable map, or use the coordinate-display device found near the Green Tower. Read 4166 and 1899 as two coordinates.
Full solution
Reveal the button location and co-op step
On the map, follow the 41 grid line and the 18 grid line. The final digits refine the location: roughly two-thirds down the relevant square and almost at its eastern edge.
Search east and south of the starter hub. A small button is camouflaged behind a rock.
One player must hold that remote button while another returns to the numbered structure and takes the reward when the glass opens. Carry walkie-talkies because the two roles are far apart.
