The printed signature on the copied Lowry images is occasionally visible underneath like a shadow.

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While this issue has been a problem on eBay for some time, auctioneers in the North of England have recently received prints purporting to be original lithographs signed by Lowry.

Genuine limited edition prints, which were produced commercially in the 1960s and 1970s and were signed by the artist in editions of 850, are now fetching prices from £800 up to £2500.

The works now emerging are high-quality reproductions of these images which include the Fine Art Trade Guild blindstamp.

The tell-tale signs include signatures that appear to be 'oversigned' - the result of being 'firmed up' with ink or pencil. The printed signature is occasionally visible underneath like a shadow - see image here.

Any Lowry work which has no verifiable provenance should raise suspicion. It is often claimed that the work - typically framed to disguise the use of modern paper - has been owned by a relative or acquaintance for a long time but they do not know where or when it was acquired.