D15 Distributor Mystery

I got a D15 gas at a consignment auction Sat. It started good but ran like it was misfiring so I looked at the plugs and they were rusty and cruddy. Also looked at the points and they were almost closed so set them to .022. I checked the plug wire positions before removing the cap and 1 & 2 were nearest the radiator. I did NOT remove the distributor and did NOT remove plug wires from the cap. Checked the compression and all cylinders are good. After installing new spark plugs and carefully indexing the dust shield, rotor and cap when installing, 1 & 2 were nearest the radiator again so connected the wires for CW distributor rotation. The engine would not start. When cranked with the #1 plug and distributor cap removed, rotor was pointing away from the radiator with #1 coming up on compression. I once had a D17 slip timing due to the gear on the governor shaft slipping (key wore out) so decided to sleep on it before proceeding. More checking yesterday and decided the distributor must be 180 out so moved plug wires in cap so 3 & 4 are now nearest the radiator. It started immediately and, after adjusting timing, runs great. The mystery is, how could it run when I bought it with the distributor 180 out? I did not change any distributor parts or remove the distributor and see no indication of recent work on the tractor, especially the distributor.
 
Running on two cylinders. Whoever put the distributor in 180° off knew enough to fiddle with it until it would run on two cylinders but not enough to know what they did wrong. Chalk it up to "stuff happens".
 
Sounds like someone 'worked' on it at the auction,unfortunately it pretty common for people that want to buy cheap to mess with a tractor so it won't run right.
 
I checked before doing anything and it was running on 3 (no difference with #1 plug wire disconnected) and no evidence of any tampering at the auction. My theory is that the rotor was not indexed and must have been around 180 away from the notch. The installed cap then put enough pressure on the rotor to cause it to cock enough so that it didn't slip. The rotor button that contacts the cap was very rusty indicating to me that it had been hot enough from friction to burn off the plating and that it had been this way for a long time.
 

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