Just to raise Bodston's blood pressure a little
.:
No, seriously, somebody post one that's actually possible.
(Though if anyone really can work out, or have reference to, exactly what this is there's a few of us that'd be fascinated to know... Bovington tank Museum amongst other luminaries have been asked but seem to remain largely puzzled... if you
really think you know what it is, make sure you have a very thorough double check.)
Cheers,
Adam.