I was wondering just the other day why some of these were made in mils and some in degrees circa WWII. Artillery use in mils?
Damn good thread by the way!
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I was wondering just the other day why some of these were made in mils and some in degrees circa WWII. Artillery use in mils?
Damn good thread by the way!
Some/most British Army Mk3 compassed were upgraded to Mils but might look for all purposes like old 'as made' Mk3's. Some of the oldies still have radium but they're few and far between now but they all have the little trefoil on them and Ra133 for radium and T for tritium. Talking of mils, some of our Binos, prismatic No2 Mk3's are now graduated in mils instead of degrees.
As I mentioned somewhere else, the oldest EMER I can see dates to 1955 or so (sorry if I said 1952.......) and makes no mention of a guardless variant. Maybe we sold the guardless cheapo variant to you wild colonials of savage Antipodeans...........
All British fire control instruments (as far as I know) were made in degrees at this time. The NATO interoperability agreements caused us to abandon or update them.
A bubble makes them useless. It's better to have it empty than bubbled. I'll explain the ins and outs of de-gassing when I do the whatsit article. Bear with me. I've got to get a couple to write off first
As a matter of interest Son, do you have an RAEME Instrument shop there? Are you still using these prismatics? We had them in Aust. Malaya and SVn as I recall
My understanding is the mils thing came in in the mid 1960's for most NATO countries. The reason is simple - mils are easier in terms of mental arithmetic when figuring out artillery coordinates. The original MkIII degree dials were all semi-transparent mother of pearl. This is so that the low-intensity radium lights would illuminate through the dial at night. The modern dials are not, I believe, semi-transparent. They are made of something other than mother of pearl as well and are still produced in both degrees and mills by Francis Barker who still supplies the spares to MoD. They also make dual-use dials in both degrees and mils - I have no idea if MoD uses those or not.
Given that the radium is long since worn out, I rather suspect the compasses held in MoD stores which are actual mkIII's vice later M73 compasses, have been rebuilt several times over now. Peter tells me some are still in degrees for training purposes when non-NATO countries come to train and work in degrees. Most I suspect are long since converted to mils and although the earliest M73's have mother of pearl dials, I'll bet most of the dials in use now are not the MoP type unless they are degree compasses. I really wish my compass were a MoP card version (it used to be), but the only replacement available for my cracked one was a new made francis barker degree card. Functionally that is a good thing as the old dials were only accurate to 1.5 degrees while the new cards are accurate to 0.5 degrees.
Another interesting tidbit is that not all mil cards are the same. Some are 6000mil some are 6400mil depending on which country issues the instrument. NATO countries all use either degrees (uncommon) or 6400 mils.
Without confusing things too much for ppl who don't understand mils, there are 6283.1853 mils in a circle, but the U.S. military standardised this to 6400 mils (to simplify math), so that North is seen as 6400, South is 3200. There are two pi radians in a circle, where pi is 3.1416.... One pi radian is a segment of a circle that has a rounded edge that is the same length as the straight sides and from the radian we get the mil, or mil-radian (approx. 1/1000 of a radian). Mils are now used because an angle in "x" mils is "x" units wide at a distance of 1000 of the same units. In other words, at a distance of 1000 metres, a 3 metre long object will appear to be 3 mils in length.
Since this is all based on guestimation of an object's length at a given distance, it is not a perfectly precise method, but it IS more accurate than degrees out past 500 meters or so because the unit size is much smaller. And because it only needs to be "close enough" no country actually uses a compass in 6283 mils.
Now to really confuse everyone, the French use a totally different and unique system calls the "GRAD" system where there are 400 divisions on the compass (vice 360, 6000 or 6400). I have no idea how it works, so don't ask! LOL.
Interesting. When you pull your two compasses - would it be possible to try to get two earlier MkIII's (from what's available) and try to have one with radium and one where the lights have been upgraded by removing the radium and substituting Tritium? The early MkIII's are interesting in that the backlight cup was designed for the radium paint and it would be great to see how MoD officially converted these.
As for the Canadian Army, in WW2, F-B allowed Canadian Kodak Company to produce them during wartime only (a patent issue) so we (Canadians) marked into Europe with domestically produced MkIII prismatics, though I know some Kodak's ended up in UK stores and some FB's in Canadian stores. An interesting fact is that regardless of maker markings on Brit compasses, all parts were made by Francis Barker and the maker refers to the ASSEMBLER. The "B" prefix on brit made compasses stands for "Barker" to show they made the components.
I've never seen a non-upgraded Kodak with a guard. I did see one, but it was a Canadian issue compass upgraded to mils so the guard was a retrofit in all likelihood. All Brit compasses I have ever seen with guards that are still in degrees were made after 1943. I know this isn;t definitive based on the small sample size, but a LOT of pre-1943 MkIII's have no guards on them from the photos I've been googling and the examples I've personally handled.