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Hi Andy,

Thank you so much for the pictures! The prism looks entirely like the original part from Freiberger. I don't think that there are any generic non-Freiberger versions of this highly specialised accessory that are identical in shape and form and use the exact same mounting mechanism as the original Freiberger part. I am surprised about the low price you paid for the prism. Given the price of the Cassens & Plath pentaprism and what I assume is the relatively high accuracy of the Freiberger pentaprism I would have expected much more.

The certificate is most definitely an original Freiberger one, as the same signature (difficult to read but maybe "Böhmer") can also be found on other certificates from the period.The fact that the error of the pentaprism is not noted on the certificate might indicate that the sextant was originally supplied without one (do you know whether the firm you worked for used the pentaprisms?).

It is very unusual that a Freiberger certificate contains no date, but given its serial number, it seems certain that the sextant was produced in mid-1978. Correction values ranging up to 60 arcseconds seem also unusual for a sextant employed in a Western country. Maybe my impression that mainly copies with low correction values were sold to customers outside the Eastern bloc is not entirely correct, or this rule did not apply to sextants intended for surveying, as surveying by sextant did not require the same accuracy as astronomical navigation (at least the different specified accuracies of the SNO-M sextant and its SP surveying version seem to imply as much, see Paul's message and pages 6 and 22 of https://hydrography.pro/presta17/index.php?controller=attachment&id_attachment=53). Or the survey firm bought sextants with domestic specs directly from the GDR, saving some money, who knows...

Do all moving parts of your sextant, including the drum and drum locking mechanism, move freely, or has there been some maintenance in between?

Regards, Martin