A web search suggests that Hilger & Watts seems to be a manufacturer of
surveying instruments.  This may be a collimator which is a device to
ensure that a surveying instrument is positioned over a station, sort of
an optical plumb bob.

Doug Welch wrote:
> 
> I have just recently picked up what I believe to be
> a seismograph made by Hilger & Watts (SG 416). However,
> it has no manual and I am keen to locate documentation
> (or at the very least, its detection characteristics).
> Can anyone on this list help (or provide a good lead)?
> 
>

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