Hi Mike,
PASS-- sounds like your Mate is not being a stickler for authenticity on this job.

If the Direction of Rotation, drive type, ie, tang drive or coupling--some automotive engine ones do not have an impulse but a straight shaft for a flex disc, and flange with pins and so on.
I have used parts to fix Eisemann Mags. from straight shaft car Mags. and so forth--mix and match what ever fits with the correct attachments and so on.

If you are not a stickler for authenticity or just wish to make something mobile then a Fordson Simms Mag., International, FBM, Bendix, Bosch, Simms or other branded Mag may work--my 1st 2 Ton had a Fraudson on it when I got it.
I made a very large International Tractor 4 cyl. mag. work on the pony of my RD6 to get it mobile and home until I could overhaul the tired Eisemann. Simply reversed DofR, and ran wires to earth for the plug wire towers not needed.

Currently have a Chinese, Arqin Bruiser, knock off a Honda Rebel 250cc, running on a 4 cyl mag. converted to coil Ign. way back by someone--I found it in a dumpster way back too--I set it up to be driven straight from the crank (correct DofR) with a piece of fuel hose, hose clamps, and suitable adapters, G clamps, blocks of wood--two outlets earthed and we are away for a test run--bike had only done, by the odometer and tyres looks correct-- 1,300 odd Klm's (800 odd Miles) from New and the Alternator burnt out solid state components in the regulator--am told that they need the Alt to be operative for Ign. to work???
Got to the back of the circuit board bit after chipping out epoxy on that easy to get at side. The component side is in some sand filled harder goop that blunts tools and is face down in blind finned alloy case--may need to mill that side and see if I can get further in to see actual components to replace. May use automotive Reg but not sure if higher charge rate in one of those may fry any good Ign. bits--electronics are not something I know about other than if the smoke escapes it is no good--this things Regulator Board smells cooked and left a stain in the goop.

May need to find my bottle of Spare Lucas Smoke to put back in the circuit
Bike was found in a Scrap yard for free, due to no parts being available--am told Honda bits fit if your wallet is full enough--engine runs nice--now to build our own electronic Ign. system--maybe!!!

What ever ya got and it fits with the criteria met you are in business--gotta be resourceful sometimes )

I think one of the scans had the Interchangeability of parts between Eisemann Mags.

I guess to properly answer your query I would need to see the iron--Engine and Mag. to check the above.
Mags are built to fairly standard dimensions and so can more often than not will interchange--see scans below that I got from Smokstak site if I recall.

Cheers,
Eddie B.

Hello Eddie, thanks for taking the time to upload those extra scans, as you say, anything could be made to fit if you have the time, and brains, the first component I have plenty of, the second component I'm a bit light on..... Ha ha

You would have noticed that interesting magneto on a recent post on a 2 Ton engine with the Hall Scott rocker cover, the spark wires did not come from the end of the magneto, but from the middle, I'd never seen one like that, do you know what type of mag it was?
All the best
Mike

Since you guys are om Mags perhaps you could give me some advice on my Cat 15--pulled the plugs and have no spark---two of the plug wires have no continuity
I want to pull the mag off and have a pro check it out but have no idea on how or where to disconnect it and can it be marked so the timing will be correct when i reinstall

its a fairbanks morse---type fm---j4a11 and its nothing like the manuals show an eisemann

depenzic, When I removed the mag from my 22, I made sure it was on #1 tdc. The timing marks are on the front pulley (I think the 15 is the same) but to make sure I pulled all of the plugs to turn the engine easily and did the thumb over the #1 hole to verify that I was not 180 out. When the mag came back, I could not figure out how to time it. The cap had a window (yours may not) to tell when the rotor was at #1 but the coupling was 30 or 40 degrees off. I talked to Old Croak and they said that if it ran before it was removed, it should go back on without adjustment. I still could not get the coupling to line up, so I finally turned the motor backwards until the coupling lined up and then turned it back to tdc (or the mag mark, I dont recall) and the impulse coupler snapped and it turned out that everything was OK. The impulse coupler made it too hard to line up when installing at tdc. Old Croak said to make sure that the shaft coupler was not tight against both halves. It causes a bearing to wear out. To clear this up a bit, the impulse coupler is inside the mag and you dont see it. The coupler that joins the mag drive shaft from the governor to the mag is the one that you line up.
I hope I have not just confused the issue . Grant.

oldcroak.com/eisemann-cm4-ct4-magneto-instructions/

Niel, my 22 has a Wico mag so I dont know if there is a way to disable the impulse coupler. Old Croak told me that the Wico is plenty reliable and hot, and that is what I have , so I will stick with it for now, but I agree that the Eiseman is easier to deal with and more common. Adjusting points with a mirror on the Wico is not fun. Grant.

Hi Mike.
it is a Fairbanks Morse RV/RX Series Magneto--yet again Googling "oldcroak" who will tell you all you need to know about these jiggers.

oldcroak.com/fairbanks-morse-rv-rx/

Cheers,
Eddie B

Thanks Eddie, very interesting, I'd never seen one of them before.
All the best
Mike