Made in Belgium - S.A. faïencerie de Thulin

I have no idea wich factory.

I was wondering how do you date Belgium pottery? I put a pic of one of my older vases a while ago and we figured out it was an older Art nouveau period piece. I have another and was wondering how can I tell how old it is? I've done web searches and haven't found anything where I could learn to date the Belgium pieces. I often see them up on auctions but are weary about buying something a seller claims is vintage when it might have been made yesterday....not that I wouldnt want it, just not pay a vintage price.
here are the two pieces I have the yellow and green AN piece


now this little bowl...how would I date it?

S.A. faïencerie de Thulin. Model 328 size 4 production between 1923-1973.

S.A. faïencerie de Thulin.
vase: catalog model 5
bowl = Cache-pot (planter) model 5
between 1923-1973

Thank you for the look and your help with the dating