Copper headliner mesh 46' post

Counterpoise for single side band radio.

Usually the bottom of a marine SSB antenna system is tied to the water thru the boats hardware or DynaBlock.
The screen may be r f shielding for some reason.
Ensuring the equipment on the bridge not interfering with the tv or radio below. Or protecting the bridge from below RFI/EMI.

Maybe a call to Worton Creek may offer something.
Was your screen mounted with the same tude and hardware other under the deck items was installed with or looks like a different shop installed it?

Composite vessels over 500 tons will still have a counterpoise mesh installed due to GMDSS . Steel and alloy vessels don't need counterpoise for obvious reasons. I'm not sure if new composite builders like Viking and such are still installing HF counterpoise as HF / SSB communication is a relic in this age of Satellite and near shore cell connections . Counterpoise is all about gaining surface area for an R.F. ground plane to help the SSB coupler or auto tuner at certain frequencies and to dissipate the RF ground so it doesn't induct radio freq. into other items aboard . If installed properly the mesh will be connected to a Dyna plate via a wide flat copper strap or two as a single round conductor like a #2/0 battery cable doesn't have enough surface area. Ralph, I've come across loaded trap antenna's that had a ground lug but a regular SSB antenna base wouldn't be grounded but the antenna would be connected to the auto coupler via a high voltage wire of GTO 15 . Unless your going to communicate with a HF base station or ship to ship via SSB than remove or ignore the copper mesh.

Good point about receiving A.M. and upper side band for the cruisers weather net. A decent multiband receiver with a short dipole antenna would suffice for all frequencies so you can receive the time tic to the BBC. Your ground plane or counterpoise doesn't assist your transceiver on receive but only when transmitting R.F.