DC Input Elicar Macro-8 Ring Flash

On the battery box of the Elicar Macro-8 Ringflash is a red socket marked DC 6v Input only. I'm assuming this is to run the flash from the mains via an adapter. Does anyone have any further information on this socket, and/or type and polarity of the plug. It looks like a 3.5mm socket but it extends from the case about 3-4mm. Thanks in advance for any help.

Here's a link to the manual. In the specifications it just makes a reference to an optional 6V adapter.

Thanks for your reply.

I got a 403 error on the link but I have the manual, a scan of the original, but readable. I was hoping maybe someone had more details on the socket. The flash works ok on my *ist DL2, haven't tried it on the K7 yet but assuming if it works on the *ist it will be ok on th K7.
I realise its an old piece of kit but it's amazing the stuff people have tucked away "just in case" so keeping my fingers crossed.