The fabric of the pottery sherd is known as Stamford Ware owing, unsurprisingly, to its manufacture in a number of small potteries concentrated around the Lincolnshire town of Stamford. It was produced between the ninth and thirteenth centuries; by the tenth century, Stamford was one of the major pottery centres of England, exporting its wares throughout the country. By this time, pottery would have been produced on a wheel as opposed to the earlier method of building up a vessel in a series of rings or coils. Stamford produced a variety of fine wheel-thrown vessels, mainly cooking pots, small bowls, spouted pitchers, jugs and dishes. Many of the fine table wares were decorated with a transparent lead glaze and, after circa 1150, with a bright copper green glaze, a useful piece of dating evidence for the archaeologist.
The pottery sherd from Wellingborough is unglazed and an unusually dark colour. This colour is the result of a lack of oxygen during the firing process, a process known as reduction, and is associated with the earlier fabric types. The sherd is decorated with a band of diamond-notched rouletting typical of the 10th-century examples. At just 25mm in length, it is unfortunately too small to determine the form of the original vessel.

Stamford pot
So why choose a sherd of pottery barely bigger than a postage stamp as Find of the Month? Well, evidence of Anglo-Saxon activity in this area of Wellingborough is scarce, with reported finds being restricted to a single small find of a silver penny of Edward the Confessor (Pastscape Monument 345426). So, despite its diminutive size, this piece of pottery is actually a find of significant local importance.
References:
Kilmurry, K, 1980 The Pottery Industry of Stamford, Lincs. C. AD850-1250 British Archaeology Report British Ser 84
Blinkhorn, P, 2017 Pottery and CBM from 30 High Street, Wellingborough, Northamptonshire (Site WEHS17) In AAL Report AAL2017019
Regia Anglorum – Anglo-Saxon and Viking Crafts – Pottery
University of Leicester website