It’s likely from the 60’s and could sell for $5-$15 in an “antique” store.
A tough sell because Peanuts collectibles are very plentiful, and glass/pottery people are more refined in their tastes.
Aside from the Peanuts bobble heads, not many things from that era have big resale value.
I think you are probably right especially on the date. I just noticed the little gold sticker on the bottom says “Made in Japan”. It is in very good condition, if one didn’t know better you’d think it was pretty new. It does have “Schulz” signature on the side but it appears to be a stamp or screen print perhaps, under the glaze.
That very day we made our planned trip over to Alexandria, which is known for it's antique shops.....they'd already doubled up the prices on his memorabilia.