Hi David,

Looks like the repainting may have included an error in the number. If it's 0 gauge, the Loco number should 4020, the '4021' painted on the cab indicates a Gauge 1 loco but that's quite a bit larger again. From what I can see, your example does appear to be 0 gauge as you state. I guess it was repainted due to the original paint being in poor condition, quite common with live-steam models due to the heat and spillage.

So from what can tell, the correct catalogue code should be "H 4020" for your model but someone may be able to clarify. I've attached a page from the UK 1929 catalogue showing the G1 version which is the closest I could find to yours but even then the Tender is not quite right (bogies).

Generally they show just one with the assumption the other version is much the same, just smaller or larger as the case may be. Take the Boiler rings for example, the G1 has 6 rings, yours has five. Probably kept the same spacing, just dropped one to keep it looking visually balanced.

But if you google "Märklin H 4020" and also "Märklin H 4021" and then select images, you'll quickly see other examples. As for demand, well of course there's always interest, but with items like this condition can be everything. Yours has been repainted and not accurately so that would put many collectors off. Ironically, many would prefer a tatty original, than a repaint, no matter how well it's done, but much worse when done incorrectly. But of course it could be a late great-Uncle that repainted it, using whatever materials and skills were available and it's still part of the history of the time.

Hope this helps

Cheers