I've done a little more research on where the Snake Clasp was found.
It came from a deposit which dated to 1838-1851. It was found in the underfloor deposit in the rear room of an extremely small tenement. The house was tiny, probably only two rooms. There was a police constable living there in 1845, unfortunately we don't have occupation records before that date, so he may have been there since when the house was built in 1833.
As far as I can ascertain, the context dates are too early for any Colonial Military units to have used the clasp, but until 1870, British Garrison Troops were here, and until 1848, their barracks were less than half a km away.
I've found that British Police also used them, but so far I've only found them on Inspector or higher uniforms.
It's interesting that this example has a head and a tail, and the tail is slightly smaller and looks a little like it may have a rattle, like a rattle snake. So far I haven't found any examples like it.
Any advice from this wondrous store of knowledge would be very gratefully received
Cheers
Mon