These pressboard plates have mailing labels on the back which call for 6 cents postage.
They're fancy postcards.
If they fit into the 2 ounce first class postage rate (I didn't weigh them), that would put them before 1958. That's a three year window after the opening of Disney Land.
That feels about right stylistically. The artwork is loose but still "appealing". Moreso, in my opinion than the animated versions of these characters.
The brush line makes them feel more like Carl Barks' great drawings than the tight motion picture draughting.
Even how the Goof lays out interrupting the frame line is a nice design touch.
I got this exacerbated Donald for Christina. Seemed appropriate.