29th May 1761 Bout of Mr Venables at the Sign of the Beaver Piccadilly a Fine Beaver Hatt 21/- A Hatt Turning ..18d
Paid him for it before young Wade of Retford his apprentice.
I've found mention of a Mr Venables of Piccadilly - he was a subscriber towards a 1795 edition of Pilgrim's Progress.
Beaver hats were made initially from European Beaver but by this time most seem to have been made from pelts imported from North America. More here.
This hat seems likely to have been a tricorn - Some eighteenth century men's fashion is displayed here.
Thomas seems almost always very concerned that it is clear that he has paid. I find it interesting that he buys from a hatter whose apprentice is from his own home town. So often we seem to think that people didn't move much in the past but Thomas has many contacts who are spread over the country.