This is probably an original survey heliotrope. I obtained this from a small antiques shop in Antwerp where it had been gathering dust for many years. The seller informed me that it was originally obtained either in Sri Lanka or Myanmar (Birma). Considering it is of Dutch make ánd obtained not to far from Indonesia it is reasonable to suggest it was used in the triangulation of the Dutch East Indies, now Indonesia. However no certainty.

The actual age of the instrument is unknown but again considering these instruments were not in use before the late 19th century and were no longer required in the 1980s it is from somewhere inbetween. It probably dates to somewhere before or just after WWII. The instrument seems complete in a box. If the box is original I do not know. The mirror does not fit into the box; however it could also have been that the box has dried out over the years.

All parts are numbered '10' and seem to belong together. The operation of the instrument is quite simple. Using the circle and crosshairs the surveyor is sighted by the 'heliotropist' from the target location. This is not very accurate, but the beam of light is usually big enough to cover any inaccuracy. Later models had a telescope rather than a simple viso as this one has. The mirror can be rotated away for sighting. After that the mirror is rotated back into location and using the image of the crosshairs on the circle is aimed. As the sun moves (15 degrees / hour), the mirror needs to be kept in adjustment. According to other sources this was done using a hammer; this is however not supplied with the instrument.

More information:

NOAA

The American Surveyor