Just got my MkIII Compass back from Trademark London

[MrBurns]

Hi all, I've been reading your discussion on compasses, and as a collector of British militaria, it looks as though I've stumbled into the right place. Anyone know anything about J.H. Steward compasses made in 1900? I bought one with leather carrying case and inscribed TH Lovell on ebay years ago, and it looks like the ones in these pictures, only much older/less fancy. the compass card is brown paper with mother of pearl on the outside edge. unfortunately, the compass needs work- the card doesn't turn freely. any info on its history or where i can get it working again would be greatly appreciated. Cheers, Greg p.s. still trying to figure out how to imbed a picture. any thoughts

---------- Post added at 08:39 PM ---------- Previous post was at 08:29 PM ----------

Hi all, I've enjoyed reading about compasses- looks like I've stumbled into the right place! Anyone know how/where I can get a Boer War circa 1900 J.H. Steward compass fixed? Mine looks just like the one's in the photos, but of course, much older and simpler. I bought it and its leather case years ago for my Boer War collection, and would like to get the cardboard/mother-of-pearl card working again. I can post some pictures once I figure out how. Any help/information would be greatly appreciated. Cheers, Greg

[Claven2]

Hi Greg and welcome to the site. I would recommend posting a photo or two of the compass and we'd be able to better help you. On the surface, it woulds like a pre-WW1 marching compass. If so, they are designed to only spin freely when the release button is pushed. Have you tried that? Marching compasses normally have the card not in contact with the pivot except when you take a reading. Finally, I assume it has radium paint, not brown paper on the card. I would enjoy that compass by not storing too close to where I sleep.

For off-sit picture linking, read here:
https://www.milsurps.com/showthread.php?t=28922
Or if you want to upload pics to this site directly, look here:
https://www.milsurps.com/showthread.php?t=10721

[Paul S.]

Both of my Prismatic compasses have suddenly developed bubbles. They've been put away since I last used them, pulled them out this Arvo and... Looks as though Trademark and I will be doing a bit of business in the near future.

[trademarklondon]

Hi all, I am Paul from Trade Mark London

I've just read this thread, I wasn't aware of it in the past, and I've also posted a comment to Peter's advice for servicing prismatic compasses, which I'm sure he won't agree with

I am a compass maker by trade.

A few pointers. The original design for the MkIII compass did not include lid window bars. They were fitted retrospectively where the compass bears an early date, but became optional later on, and from around 1966 when the Mk1 was introduced (MkIII converted to mils) the bars then became standard.

QMs all over Britain freely admit to having used and still using "putty" or mastic to try to fix compasses. I have never understood this, as the actual purpose made o-ring costs just pennies. If a compass leaks it is almost never because of the fibre washer breaking down... fibre washers, by their nature, just don't break down... it's failure of the rubber or silicone o-ring, which must be replaced, otherwise you are treating the symptoms instead of curing the cause of the problem.

Liquid prismatic compasses are precision instruments. Each one comprises over 120 component parts, and they are all hand assembled, balanced and calibrated by highly qualified people. The compasses are certified accurate to within one half of one degree at all four cardinal points, and that accuracy must be re-checked and certified on re-assembly of the compass, as many parts can move during servicing causing a compass to give erroneous readings. Compass servicing involves skills very similar to those of a watchmaker, and certainly we share the majority of our tools.

I don't want to start WW3 with my comments, but I would like people to think very carefully before they proceed with home servicing for many reasons. MkIII compasses contain substantial amounts of Radium 226. This substance is getting close to the Polonium used to kill Alexander Litvinenko in London a few years ago. Radium 226 has a half-life of around 1400 years, which means almost FOURTEEN THOUSAND YEARS to total decay. Think about that. From the late 1960s Promethium was used, which isn't recommended for eating, but is much less toxic than Radium, and now Tritium is used, which is fairly harmless, unless eaten in large amounts

Fluid - turps, meths, surgical spirits... all wrong for many reasons. SIRS continue to use Isopropyl alcohol for their G-150 compasses. Many believe that this substance is too volatile and aggressive on the seals, and they may have reason, because the G-150s always seemed to develop bubbles.

I use purified kerosene. It's not very volatile, so it doesn't find its way out... it has slightly higher viscosity so provides better damping, and survives temperature extremes better than Isopropyl alcohol. Whichever fluid you use, however, you MUST match the o-ring to to fluid, as o-rings made for kerosene will not survive long in contact with IsoP. Vice-versa, -rings for IsoP will last longer with purified kerosene.

Where do you get purified kerosene? B&Q, any hardware store... it is transparent lamp oil.

I could go on for hours, but really I only wanted to introduce myself and to put right various urban myths that are doing the rounds here, which will cause damage to compasses.

If anybody has any questions or comments you can address them here in open forum or contact me directly. Compasses are what I make, what I do, it's my job, my trade, and I am happy to answer any questions. There are no "secrets", but there are skills that need to be learned and mastered, just like watchmaking, I suppose, but slightly less complicated.

[trademarklondon]

I think the UK MoD own or did own the patent rights to the prismatic compasses. Long expired now I expect. And for the purposes of the strip-down we'll be using the later Stanley compasses as they're most like what we've come to expect

As a matter of interest, the bloke who designed/invented/came up with the idea of the triangular prism was the former military attache in Budapest who saw the ZB 27 being used/tested in Hungary and got two examples sent to the UK as late entrants into the trials to replace the old Lewis LMG. The rest, as they say, is history....... He was a Royal Engineers Major who eventually ended up as a Brigadier. I forget his name but his most famous contribution to the Commonwealth was the Bren of course. When I transfer all of my blurb onto this new computer, I'll dig up his name

The prismatic viewfinder was patented in London on 5 March 1812 by Charles Augustus Schmalcalder. This gave rise to the prismatic compass, and to optical theodolites and other sighting devices that we all take for granted today. The prismatic compass will be 200 years old on March 5, 2012, in about 9 months time.

---------- Post added at 09:57 PM ---------- Previous post was at 09:52 PM ----------

Where can I buy Purified Kerosene in Australia?

any hardware store, just ask for non-coloured, transparent lamp oil.

[bramble]

Hi all, just wish to say that I've recently had my G150 serviced, seal replaced fluid replaced with kerosene and not "iso"and its basically saved and restored my compass previously it had this dreadful putty which made the fluid cloudy and resulted in fluid loss, Now a happy man as it is on a daily basis.

[trademarklondon]

I have just made a 19 minute video which you can view by clicking on the link below.

The video is not a demonstration of how to service a liquid prismatic compass, but is an indication of the problems an unqualified person will encounter should they try to do it themselves.

It is a very fast, synthetic view of a job that actually takes several hours, and does not show the calibration, a skill that takes years to learn.

The video will possibly help those who want to try, though it is not intended as a guideline for that purpose, but more it is to point out the dangers of Radium 226, and the fact that once opened a compass immediately loses its calibration, and re-calibration to within one half of one degree at all four cardinal points is an integral part of servicing, and which takes specialist optical instruments and a qualified person to carry out and be able to certify the compass.

The video will also dispel various urban myths, such as using gunge to seal the glass, a special press to seal the glass to the gunge, and types of fluid to use or not to use.

<script type="text/javascript" src="http://content.bitsontherun.com/players/ENjwE5mw-8OryQgeY.js"></script>

[trademarklondon]

I have published an eBay guide with a vew useful pointers for anybody considering acquiring any used prismatic compass

CLICK HERE

If you think the advice is helpful feel free to give it a yes vote on the eBay page

[bramble]

I have just viewed 19 mins and 45 secs of excellent footage which was concise and informative and at the same time emphasize the dangers of radium and to steer well clear of damaging putty which was the main reason mine needing to be serviced. Attached are before and after photos of my G150, note also the size of the bubble, Many thanks to Paul of "Trademark London", for a job well done


Attachment 24418

[bramble]

Probably guessed had a few upload probs