Hi.
A valuable harmonica from Poland???
Well I guess anything's possible

.
I'd say what You have there is what was/is referred as a "sailors harmonica" IIRC. The harmonicas by Höfner and the like, were relatively expensive, so there was cheaper alternatives for travellers as well.
However, the fact that it's not riveted design, would suggest some level of repairability.
If that was mine, I'd pop the lids and the reed plates off, straighten the lids and give the reed plates an alcohol bath.
+1 for not derstroying the reeds by blowing too hard. Do that, and it is scrap.
Regards
Sam