Okay, I think I found the serial number. There's an ID plate on the drivers side firewall. The number is "i574-ii4307". I used lower case i's to avoid confusion with the number 1.
I also found a number on the floating axle "3412*F"
And on the transmission pumpkin "19750"
I also got some calipers in US Standard measurements this time, much better.
4.49" - Wheel Drum inner diameter
3.12" - Shaft inner diameter
4.37" - seal outer diameter non flange side without felt
4.48" - seal outer felt washer diameter
4.75" - seal outer diameter felt side
3.12" - seal inner diameter (same as shaft diameter)
1.15" - seal thickness
If possible I'd like to buy a new inner seal, ideally with improved design. I found felt washers on McMaster Carr (https://www.mcmaster.com/felt-sealing-washers
), that's an option to keep the metal seal and replace just the felt. Not completely sure how I'd get the felt in there without destroying it...