railway sign?

["Ann Tuckey" <atuckey@pnc.com.au>]

I was wondering if anybody knows if the following sign is of railway
origin,if so what it means and where it may have come from.
It is a metal sign,painted yellow,with black writing,and measures 46cm x
31cm.
It says:
                       BLUE
                         D/D
                       STOP
                       HERE
                               2'72      (numbers in small print)

Thanks,
   Ann.