Police in Bulgaria have discovered what they say is a previously unknown Jackson Pollock painting during a recent raid in the country’s capital city of Sofia.

The artwork dates from 1949 and bears the late artist’s signature on its right register, according to Bulgarian National Radio (BNR), which first reported news of the finding this week. Citing “experts,” the news outlet said the painting may be worth up to €50 million ($53 million).

On the reverse of the canvas is a detail that, if real, may justify such a lofty evaluation. There, in hand-scrawled text, is what appears to be a dedication to the American actress—and noted art collector—Lauren Bacall, Sofia’s deputy city prosecutor Desislava Petrova said during a press conference on March 22.

“Dedicated to my very talented and dear friend Lauren Bacall, Happy Birthday,” the message, believed to have been written by Pollock himself, reads. It is dated September 16, 1949—the day of Bacall’s 25th birthday. 

The alleged Pollock painting has since been transferred to the National Art Gallery in Bulgaria, the Sofia-based Novinite news agency reported. Authorities have yet to share a description or picture of it.

The artwork was one of six seized as part of an investigation into an organized crime group jointly carried out by authorities in Bulgaria and Greece. Three Greek citizens and one Bulgarian were arrested in connection with the case.

In an appearance on local television, Bulgaria’s Chief Secretary of the Ministry of Internal Affairs, Petar Todorov, called the investigation a “very successful operation,” per Novinite.

Todorov also expressed confidence that the painting was indeed made by Pollock. “To our great joy, we managed to establish and keep this painting and at the moment the expertise shows that it is an original,” he added.

That assessment is far from definitive, though. Since the 1990s, when the Pollock-Krasner Foundation disbanded its authentication board, questions over the legitimacy of the artist’s work have been directed solely to the International Foundation for Art Research (IFAR).

When reached by Artnet News, IFAR’s executive director, Sharon Flescher, said that “IFAR has not seen [or] examined this painting; nor have we been formally requested to do so.”

Helen Harrison, the director of the Pollock-Krasner House and Study Center in East Hampton, New York, similarly reported that she has not been contacted by Bulgarian officials. Harrison declined to speculate on the potential price of the recently discovered painting were it to be deemed authentic.