Dona Vietnam ceramic vase (?)

Hey, I bought this vase on the flea market in Poland this weekend because I liked its pattern with waves. It's heavy, the glaze has light signs of aging, marked but the mark is smudged. It's about 28 cm high, and 18 cm wide. The lady who sold it said it's probably 50 years in their family.
I tried to identify the producer and date but as the mark is smudged I'm not sure. Thanks to other threads here I came up with Dona Vietnam pottery, and 60s-70s. Would love to hear your thoughts if my guess is right?

 

Did you see this in your google search? https://www.justanswer.com/antiques/c55pd-dona-vietnam-vase-value-information.html

Same mark as yours. I would take the value given with a grain of salt. Nice stuff and I will have to change my idea of dating these wares.