Old Car Phone Antenna on Rear Window

Hey Gang,

I recently bought a 300SD and it has one of those old style car phone antenna(e) installed on the rear window from the previous owner. There is a part stuck to the outer glass as well as inside the car.

I want to take it off and believe it was originally adhered by using heat. Someone said if you can heat up the glass you can then remove it.

Any insight here? Would be greatly appreciated. I want to remove it but need to be careful as we are talking about 20 year old glass.

Thanks in advance!