I've never really seen a decent compromise between ground scale and model scale when representing armoured trains on the tabletop, though this particular German WWII vehicle is less egregious in that respect than most.
It could be connected to a larger train, like a normal flatcar, but it also had its own internal diesel engine and could move independently.
It mounted machine guns on all sides, and a 75mm turret from a Panzer III N.
This 1:100 model doesn't really fit properly on the N-gauge track lengths I have, but never mind.
I printed the hull on my Ender 3, and the turret on my Mars Pro, and it really throws into contrast the difference in quality between the two. I'm not one of those who likes to tinker constantly with their printers to squeeze the absolute maximum from them, and I know the Ender is capable of better, but when it's so much quicker and easier (though a bit more expensive) to get much better quality from the resin printer... well, why bother?
To be fair, the FDM-printed body looks okay at arm's length on the tabletop, so what the heck. I probably won't be printing any more non-terrain models on the Ender 3 again though.
Later...
This was called PanzerJager Triebwagen, and "triebwagen" basically just mean "rail car". I'm guessing if you hang about here, you probably already know what "panzerjager" means.
It's also 1:100, the body printed on my Ender 3 and the turrets on my Mars Pro. I've got as far as base-coating it, and I don't know if I'll take it any further than this, not in the immediate future anyway.
The problem with it is that in just about any tabletop wargame's ground scale, this particular car alone would be about 300 or 400 metres long. I think that if I use armoured trains at all, I'll just use them in 1/300 scale rather than 15mm. Apart from anything else, the smaller models will take a whole lot less printing.