Meanings of unchanging expression in English

Nothing too serious, I hope? Zaman watched him with an unchanging expression.

What goes on behind her unchanging expression I will never know.

Those eyes, with their unchanging expression of concentration and thinly hidden anguish, regarded him.

While behind him sat his assistant, one eyebrow raised in an unchanging expression of casual curiosity.

Dumbarton Oaks had taught me how to maintain the proper diplomat's unchanging expression; drinking superbourbon had been a post-graduate course.

Master Kinch nodded back in much the same way, but despite his unchanging expression there was a hint of approval in his nod.

The thought of the 'Grecian Urn' is (to quote Mr. Bridges) "the supremacy of ideal art over Nature, because of its unchanging expression of perfection."

Hermanric's downcast eyes and melancholy, unchanging expressions betrayed the gloomy abstraction in which he was absorbed.

"I'm glad I met you," he said to Pelle with his unchanging expression of gloom.

And only visitors will be alarmed, wondering for a moment if war has been declared, before the unchanging expressions all around them argue otherwise.