It looks familiar. I'd say double yarn over (dyo) followed by k2tog, k2tog, ssk, ssk. something like that.
or just dyo, k2tog, ssk, repeat.
Maybe with crocheted picot or shell edge along the edges it seems.
or, to start from one end: ssk, k2tog, yo, yo, repeat.
Something like that.
On WS rows, when you come to the double yo, purl first yo, knit second yo I think...