Compasses again

[Peter Laidler]

Compasses again.

Does anyone have an early 1940 UK Mk3, TG Co Ltd made prismatic compass. These early 1940’s dated differ from the usual later Mk3’s in that the inner bowl, the liquid container sealing glass is clamped down and sealed by a 1.5” diameter x3/32 deep x 1/8”wide externally threaded brass ring. The externally screwed down ring is screwed using a pin spanner in the two opposite 3/64” holes. Another visible sign is that the bowl is filled from the top at the 9o'clock position but UNDER the rotating index ring, via a 4BA red painted filler sealed with a fibre washer and most definitely covered with shellac varnish! Apart from that, they are pretty well identical to the later bog standard Mk3 prismatics.

In fact, until you lift the lid, it’s nigh-on impossible to tell the difference between the early ‘screw-down’ clamping ring top fillers and the later 8x screw, ‘screwed down’ clamping ring side fillers. All 3 eminently serviceable early obsolescent Mk3’s that I found on the shelf had been fitted with the top screen guard which made identifying them externally doubly difficult. I thought all of the early ‘top fillers’ had been replaced ages ago!

I asked the Instrument Shop supervisor what spares were still available and it appears that they’re all pretty interchangeable – even the complete bowl as an assembly! Looking at some of the other standard early ones, it seems as though they’d probably started out their life with early screw-down/top filler bowls too. As for early bowl spares, then only the 1/32" thick x 1.5" dia. O-ring glass seal and the 4BA fibre filler plug washer are still available but then, only at Base Workshop level.

Anyone out there got one of these early compasses?

Information

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[bouletbill]

Hi Peter, my one is a 1940 T.G.Co MkIII No.B 76579 but up-spec'd to mills, so I suspect the inner bowl is a later one. I've never taken it apart because so far it 'ain't broke'. My only gripe is the index ring will fall off , I presume the brass milled rim is worn. Any ideas ?

[Peter Laidler]

Yep, it's a worn lip on the inner edge. Although I never measured one, I seem to remember that the inside of the milled rim was very slightly tapered to match an external taper on the bowl that would press down and gently click into place and rotate to boot. We had a little press that would press these down square because you could crack the glass if they weren't pressed down square - whether others used a press is open to some debate but yep, it's loose. As a quick 'get you home' type repair, couldn't you very gently, slightly bend the lip in at three equidistant points and see if it clicks and holds in place.

In the meantime, anyone still got an early, maybe 'A' prefix serial number early TG Co fill-from-the-top-bowl?

[bouletbill]

In the meantime, anyone still got an early, maybe 'A' prefix serial number early TG Co fill-from-the-top-bowl?[/QUOTE]

Peter, from what I've read, it seems that the 'B' preceeding the serial number represents the maker 'F. Barker & sons' even though it is stamped TG&CoLtd. If that is true then there may not be an 'A' prefix ... and even if there is, it may not necessarily preceed the 'B'.

confused ?

[Peter Laidler]

Totally confused Boulet.............. We still have a couple of TG&Co LONDON degrees compasses. The earliest one is TG&CO Mk3 number A-285856 dated 1940 still with the fill-from-the-top red painted screw

[Claven2]

Paul Crespel is the guy to PM about it. If the serial number does not start with a B, it might not be a Barker-supplied compass. TG&Co could possibly have sourced variant elsewhere durign the war (?). Every Barker MkIII I have ever seen was of the 8 screw variety.

[Peter Laidler]

Looks like it's time to take my camera into work and photograph it but it's definately an A prefix, fill-from-the-top bowl 1940 Mk3 TG Co Ltd compass. I have to say that it says a lot for our Army instrument technicians and Armourers that it's still going strong after 71 years although the degrees ones don't get a lot of use now unless the foreign student courses specify them. Having said that, some of these foreign students couldn't even read a comic book, let alone a compass. Even degrees are an alien concept..........

[AndreasS]

Hello Peter , I found this one in the forest last month. it is a 1940 with prefix B . It is also already converted to mills .I tried to take it apart , but i wasn t able to get the bowl out .It has probably been there for some years , as the rubber is gone and the zinc part is badly coroded .

[DaveN]

WOW that's neat! Did it fall off a compass tree?



Just kidding about the tree. I just wonder the amount of stuff lost on D-Day alone and if some one was tasked with searching and clean up? Might be a topic for a new thread?

[AndreasS]

i guess it was left over by an exercisze . i was realy surprised when i looked down . But i wonder how long it has been there...