The symbol 'RT', to which electronic component refers?
You should hand wash it instead of washing it in the washing machine becauae if it is in the machine for an extended period of time the glue on the tape will break down from the soap and water and it will come off.
It appears to be a disc ceramic capacitor or a MOV, but that would not be in series with the mains, but either would be connected in parallel, the cap as RFI suppression, the MOV as spike suppression.
have it dry cleaned or take off the duct tape and use iron on fabric stablizer instead - you can get it at a fabric store, they sell large sheets or small strips used to iron up a hem on a garment
