Weller WTHA1 serial port

[JACOPO99]

Hi All,
I just laid my hands on a Weller WTHA 1, and it seems to have a serial port on the bottom of the unit.

Does anyone know what's for? Both manuals won't say, with one just pointing to www.weller-tools.com.
I tried to look on the website but there's nothing interesting. The software updates section doesn't have anything for this station.
They won't even provide the part number for the required cable.

Thanks.