Not very unusual, it's a Bulgin connector commonly found on vintage electronics, very sensible for it to be the version that normally gets fitted to a mains lead, that way you can't accidentality plug your 12V Turbair into the mains. Why they have used a 5A rated connector when the Turbair is rated at 10A I don't know.
Thinking about it there is a risk of a Bulgin mains lead being plugged into the battery pack, I can imagine the battery would get pretty angry if it had 240V connected to it.
Its not what you know...
in Ohlsson and Rice
Posted
One of my US colleagues put me onto this on the bay of e so a purchase was made...
Image blown up on photocopier