Hi,
I guess you are following the wrong trace. A metallic object for access control can't be an RFID chip. It has no conductive areas at all.
An I-Button has conductive areas, one for the data and one for ground. If the object you have to hold inside the receptacle isn't much larger than a PC RTC-battery (dimensions F3-type: 3.1mm, dia 17.35mm; F5-type: 5.89mm, dia 17.35mm) and also looks similar it must be an I-Button.
To use I-Button access systems without any control is pure waste of money.
Each I-Button has a unique number programmed into the chip during manufacturing. For controlled access the ID must be programmed into the control computer to accept a certain I-Button.
The type of the button should be engraved in the housing. Normally it is a DS1990A, manufactured by Dallas/Maxim semiconductors.
If there is no control at all you might purchase a couple of buttons at Mouser or Digitech for far less than you paid until now.
It wouldn't be wrong to post a picture of the "key" here too.
Boncuk