It's hard to tell. Sometimes those older pieces have wood veneer (ie very thin layer of real wood) on the outward facing surfaces, you need to sand this very very carefully, if at all. If it's a mass produced piece it's quite likely that it will have some parts solid wood, some parts wood veneer, and some internal parts will be like 'sheet wood'/balsa wood (ie has no grain, is a Matt finish)
You can sometimes tell if it's wood veneer by looking for tiny places where it's chipped away and you can see layers underneath.
In my cabinet I posted above, the top is 'real wood' and solid (pine) so could be sanded merrily; the three sides sides were solid too, but the doors were sheet wood with additional detailing added. (That was fairly modern though and valueless)
I've had mass produced wood veneer retro type stuff where eg drawer fronts are solid wood but the main unit was veneer. Wood veneer is very difficult to restore to natural wood, which is why so much retro stuff gets ruined painted.
It might help if you can identify an era and a maker as you could find specific advice online about what it's likely to be made of. Or join Facebook groups for that era, I'm on a few retro ones that are very knowledgeable.