A plug connector system comprises a first plug connector and a second plug connector. The first plug connector includes a first shield defining an engagement portion, with an outer side of the engagement portion having a marking positioned thereon. The second plug connector includes a second shield defining a receiving portion for receiving the engagement portion of the first shield. The receiving portion includes an opening formed therethrough and positioned such that the marking of the first plug connector can be arranged entirely within the region of the opening in a mated state of the first and second plug connectors.