I am a compass maker by trade, and this article, while obviously written in good faith, gives fatally flawed information that will lead people to carry out work on beautiful, precision instruments, that will do such damage as to possibly render the compass beyond economical repair.

Over the years I have been asked so many times to repair bad servicing that I have lost count. I often wondered why on earth people would use putty or mastic instead of the 20pence purpose made o-ring that would be correct for the job. Mastic destroys the compass, it weeps into the fluid and coats the interior in such a way that it causes incorrect operation of the instrument. Basically it makes a mess and cam never provide a good seal, and for the compass maker who has to repair the repair it takes hours to remove. It is not just amateur, it is criminal. To seal the sealing glass you use a purpose made D profile o-ring that costs pennies, nothing more.

Special press to press down the sealing glass and mastic? Not really

Surgical spirits? Not really

PLEASE, anybody who has a G-150, and M-73, a MkIII or any other wonderful precision instrument, PLEASE do not follow Peter Laidlericon's instructions. I am sure he wrote them in good faith, but following those instructions would be like taking a Rolex watch to the butchers to be serviced... you WILL end up very disappointed and with an instrument that will probably then cost more to put right than the actual value of the instrument.

Peter, if you want me to re-write the article for you, and re-post it under your name in such a way not to unwittingly lead people to wreck their instruments then I would be happy to do so.

The average liquid prismatic compass comprises over 120 component parts. Working on these compasses is comparable to working on a wristwatch... you need special tools and to treat the instrument with respect and a delicate hand.

There is the QM's method of "repairing" compasses, and there is the compass maker's method... one leads to tears, the other leads to an instrument that will survive wars, arctic and desert conditions and that will last so long it will be passed from generation to generation as an heirloom.

I realise this is a fairly judgemental "first post" for a forum FNG, but the article will lead people to unwittingly destroy their compasses.