Who am I

My mother has lent me my great Uncles Paul P. Steven’s inventories of all he owned pre 1943 for insurance purposes. He died about that time. Above is an Attachment saying who he believed Captain Vlieland in the portrait was. I thought it was nice to see it in writing rather than my memories of what my Gran told me. 
If it is correct then the picture is of Jan Hollander.

It is painted on paper. One English dealer, ( an expert in water colours), thought from the type of paper it was on and pigment that was used, that it was painted in the late 18th or early 19th century. Defiantly no master. Probably an ammeter as not that well executed. It is square but mum had it mounted and framed 35 years ago. For many years it lay unframed in a cupboard. It is quite small, about post card size, perhaps 10 cm by 7 cm. Defiantly in the family in 1900 when the family lived in Bath. It was thought to be old then. Alice was very proud of it. It hung in her best room and was pointed out to all visitors. Another mystery which one day we might have the answer to but unlikely! The fact he is reading a book tells use he was literate, which was not that common in Britain in the poorer classes around 1800, so he must have had some degree of education and be of the merchant classes, not just a basic seaman 

So we asked the Netherlands Institute for Art history if they could tell if it was Dutch and what time it was painted and if they noticed anything else about scarf , clothes , chair or book .

They told us 

It is hard to tell anything about this aquarel based on a photo.
It is hard to tell if it is just a portrait ,it could be part of a bigger painting.
The costume does not look Dutch and not 19 century,but more a fantasycostume referring to older paintings