The beautiful face with lips slightly parted and a shimmering androgynous appearance is eerily familiar. It could be the cousin of the world-famous Crosby Garrett helmet, which a small museum in Cumbria raised an astonishing £1.7m for last year, only to be outbid at auction, sparking a continuing controversy over protection for major archaeological finds in Britain.

Tullie House museum in Carlisle is being loaned the Nijmegen helmet for the opening of its new Roman gallery next week. It is one of the treasures of the Valkhof museum, at Nijmegen in the Netherlands where it was excavated, but they agreed the loan without hesitation. Other loans are coming to the gallery from the British Museum, and private collectors.

Like the Crosby Garrett, the Nijmegen helmet is silvered with gilt eyelids and lips: it would have given the wearer an unearthly beauty.

“There can be no doubt that these helmets were made to awe,” said Tim Padley, keeper of archaeology. “The wearers would have appeared shining, inhuman, terrifying. When the Roman cavalry came through it would have been like nothing the locals had ever seen before, like the Edinburgh Tattoo erupting through your small village.”

Museums across Europe know the story of the Crosby Garrett helmet, found by a metal detector last year in a field in the Cumbrian hamlet, and the heroic efforts of Tullie House, supported by grants and donations including from schoolchildren, to acquire it.

“I didn’t have to persuade Nijmegen, they showed me their collection and when I chose this, the most beautiful, they didn’t blink,” Andrew Mackay, collections manager at Tullie House, said. “When this has to go home, we have another coming. We have managed to arrange some stunning loans for the new gallery, and there is no doubt that this saga has helped us.”

When news broke of the most beautiful helmet ever found in Britain, and one of the most complete from the Roman empire, it made international headlines.

Its fate exposed a gaping hole in Britain’s protection for archaeological finds. If gold or silver it would have been declared treasure, the finder and landowner compensated, and museums entitled to acquire it. But the bronze was not treasure, and so the finder sent it to a Christie’s auction last October, where its mesmeric beauty drove the price far beyond the top estimate of £300k. It was eventually bought by a still anonymous UK collector for £2.3m. Many of the country’s most senior archaeologists wrote demanding a review of the treasure law, which the government has promised but still not implemented.

Although the Carlisle museum has an outstanding Roman collection, the Crosby Garrett helmet would have been the star of the new £1.5m Hadrian’s Wall gallery, opening to the public on June 25.

“I have written repeatedly through the auction house requesting if not a loan, at least to be able to take measurements so we could create a replica, but we have heard nothing. We still have absolutely no idea who bought it,” Hilary Wade, museum director, said sadly. “We would really love them to get in touch.”

Roman Frontier: Stories beyond Hadrian’s Wall opens at Tullie House museum in Carlisle on 25 June. The Nijmegen helmet will remain on display until October.