I picked up Simplicity 5303 from the creative re-use store
It's from 1981--so incredibly from 1981, from that largely forgotten time when it was Trendy Youthful Fashion to wear ruffly shirts and knickers (American definition thereof), or ruffly shirts--with built-in neck bows--and A-line skirts for A Professional Look.
Which is, of course, not the kind of shirt I've made from this pattern.
But, my many deviations do lend a certain air of 'knock off Gunne Sax' to it.