Here's a painting I picked up a few years ago at a local thrift store. It's one of my favourites. It's oil on canvas, about 60 X 80 cm. Signature is on the lower right. There's a label on the back, very faint and faded but here's what I could make out: "V. KOSSUTH LAJOS TER 12" "Magyar Nemzeti Galéria" "Biralati Csoport" Lots of craquelure, and the frame has seen better days, but I still like it.
Here's a photo of the label Debora. It's really hard to make out a lot in this photo - it took me a long time in various lighting conditions and angles to decipher what I did letter by letter.
Here's some more identifying markings. This is just below the label on the back of the canvas. A circular stamp and some numbers that may be some type of inventory number.
Kossuth Lajos tér 12 : ethnographical museum Magyar Nemzeti Galéria:Hungarian National Gallery both Budapest. the sticker looks like one of these they often used to mark "free for sale and export" as surplus. Grünwald may have been member of either a German minority or Jewish. in both cases, but at different times, they were not loved...
Based on a quick search, it looks like the Hungarian National Gallery was located at Kossuth Lajos tér 12 from about 1957 to 1975. https://cultura.hu/kultura/a-magyar-nemzeti-galeria-60-eve-nyilt-meg/