Bo did a very great job to us all. I will post his pictures and comments here. It shows exactly the differences between the gauges.
Thank you very much, Bo! Well done.
His comments:
1. First kind, sandcasted, used #1- at least #388, has a special metalbase and a the first kind of gear. There might be other differences but I´m not going to disassemble my gauges at this time to figure out. You can´t use later bases and gears together with these parts.
2. Second kind, sandcasted, used at #389? - #1500? Second kind of metalbase and a second kind of gear. You can exchange all later gears with this kind of gauges. I mean, if someone finds a brand new K0 gauge with a diecastgear, it´s possible to exchange gears and get a NOS gauge with the second kind of gear.
3. Third kind, sandcasted, used from around #1500 – high #11000. Third kind of gear and the same metalbase as second kind. Exchangeable with second kind as mentioned above.
4. Fourth kind, diecasted, used at high 11000 and the rest of K0 models. Since most of this kind was produced there might be some brand new of these stored somewhere out there. Exchangeable with the second kind as mentioned above.
The pictures speak for themselves: