EMD SD70M 7000 Demo Roof-top Beacon

Looks to me like EMD SD70M Demo No. 7000 has a beacon or strobe atop the cab roof. Can someone confirm whether this is a strobe or an antenna (GPS?). Thanx!

I checked a photo I had of CSX 4675 (ex-EMD 7000). The photo angle did not allow for any roof detail. So the question remains.