Thom1995075 How come this has a classic plate? How does it work in Poland?
Oldtimer is a bit of misnomer. For most people a yellow plate is for an old timer, however if you own a collection (Museums for example) can also get these. It's actually pretty intricate. I'm sure someone else can explain it better though!
NonceSlayer's explanation covers it pretty well. Basically oldtimer plates are not only for vehicles, but also for vehicles that are historically significant (things like driven by celebrities), have any stand out characteristics (e.g. the last R34 ever produced) or that are considered a part of a private vehicle collection (but this one sometimes gets abused). So theoretically you could register even a 2022 Transporter on oldtimer plates if e.g. you own a collection of every generation of the Transporter.