Moore's marble: £1m for early 8-inch sculpture

The single, handwritten line in a household accounts ledger, sandwiched between the purchase of a refrigerator, a sewing machine and a beige stair carpet, held little clue to the item's future value: "November 31 H. Moore statuette £18, 18 shillings." Its owner chose to spend more on a chandelier (£25) and a dining room carpet (£19, 3s).

But 74 years later, an early work by Britain's pre-eminent 20th-century sculptor, Henry Moore, is expected to fetch £1m at auction. Mother and Child (1931), described by the artist as "one of my best earlier pieces", will be offered for sale at Bonhams auctioneers in London next Tuesday. The auction house says half a dozen serious buyers have shown interest in the tiny figure - just 83/4 inches (22cm) high.

Brilliant aquamarine veins run through the glossy, mottled, bottle-green marble sculpture of the mother enveloping her newborn infant in both arms. The last time the piece was seen in public was 1968, when the Art Council's director of art, Gabriel White, described it as "unique and irreplaceable".

One of only five works that Moore cut from the finest marble, verde di Prato,Mother and Child was first bought from him by Sir Eric Maclagan, director of the Victoria & Albert Museum, in 1931. The attachment the collector felt to the piece is apparent in letters between the two men from 1946, when Moore wanted it to be loaned to an exhibition in New York.

"I have hitherto refused to lend it," wrote Maclagan, "not out of selfishness, but because I am so much afraid of that soft and highly polished verde di Prato getting scratched." He added: "But I could not refuse a request backed by yourself that I should lend it!"

The sculptor replied days later, reassuring him: "I hope no harm will come to it. Being so small I do not think it should get clumsily handled."

The theme of mother and child would obsess Moore for 60 years. It was produced at a peak in the artist's talents and is said to have influenced much of his later work. He admired its "vitality" and organic form.

Matthew Bradbury, director of 20th-century art at Bonhams, said the high price reflected the quality of carving - exceptional in a young artist (Moore was 33) - and the current strength of the sculptures market.

"It has outstanding ascetic appeal," he said, "and there is the matter of its formidable provenance: the fact that Maclagan, one of the most important directors of the time and a champion of 20th-century sculpture, bought the piece from Moore ... Although it measures under a foot, its size is a strength."

The record price for a work by Moore stands at $8.4m (£4.9m), set at Sotheby's in New York last year for Three-Piece Reclining Figure: Draped (1975), a 14ft-long bronze sculpture.