Mystery Object from Ulcombe

Any suggestions would be welcomed on the purpose of this stone object which was found whilst fieldwalking at Ulcombe. The dimensions are 17cm long x 12cm wide x 10cm in depth.

The stone appears to be of quartzite type composition which is unlikely to be local to the area. The most noteworthy features are a series of 'peck' marks on the 'upper' surface in an irregular arrangement. One side is slightly curved and the 'base' is flat. It has the appearance of being 'ancient'. It may be a type of quern or millstone but is not near a known mill site. It was, though, found within 100 metres of both an Iron Age and a Romano-British site.

Any ideas would be very gratefully received.
Neil Aldridge, 31 Forge Lane, Headcorn, Kent, TN27 9QN.
archaeoword@ukonline.co.uk