The 10in (25cm) figure with a small 'fleabite' chip to the ear', was part of a very small series produced by the artist with his associate at Poole, Beatrice Bolton, in the late 1970s.
The vendor and her husband were holidaying in Dorset in 1979 when they saw both this naturalistic model and its mother on display at the Poole factory. She had wanted to buy the larger model but had settled for her 'offspring', priced then at £180.
Just one other rhino calf is known to exist and its owner was determined to make a pair, but an attempt to reunite them was thwarted by a local collector of the works of Guy Sydenham prepared to go well above the £800-1200 estimate.
The whereabouts of the Sydenham-Bolton rhino cow - on display in a photograph showing the Queen and Prince Philip at the Poole factory in 1979, shown below - remains unknown, but it seems in the wake of the sale on May 19 it may soon come to light.
Auctioneer John Condie was remaining tight-lipped but was hoping to find it in time for the firm's November Poole Pottery sale.
The buyer's premium was 15%