Watercolour on ivory signed with initials in gold on the obverse by Bernard Lens 111 who was the first English artist to paint on ivory in the early 18th c. Baroque style after Sir Godfrey Kneller.  Period turned pear wood frame (oft used for his portraits).  The new backed reverse has writing alluding to the sitter's name but is unreadable apart from 'Our .... of .....' It is in the style of Kneller's portraits who was all the rage up until the 1710s therefore I think it is an early rather fine work of Bernard Lens 111. There are collections of Lens' work in the V&A museum. He was a contemporary of Hogarth belonging to the same Rose and Crown club. He is described as "half in the old world of traditional limning and half in the modern artistic world of the 18th century." Katherine Coombs - The Portrait Miniature in England pub V&A Museum '98. This is a rather old fashioned portrait for the later 1720s to 30s. 
Frame height 12.5cms width 10.5cms. Pic height 8cms x 6.5cms.
Ivory Act Submission reference FXLN8AFQ