Looking at the data

Some things became clear as I looked at the paintings I found.

There are patterns in the signatures:

1. Wybrants [Date]
2. Wybrants - Artist [Date]
3. Wybrant - Artist [Date]

The paintings were sold in both the United States and the United Kingdom. At least one painting sold in the U.K. is of an American.

Paintings sold in both countries had Wybrants and Wybrant as the name signed.

The dates on the paintings (found so far) run from 1852 to 1855.

Paintings sold in the U.S. date from 1852 into 1853, and one in 1855.

Paintings sold in the U.K. date from 1853 to 1855.

Paintings of the men, sold in both countries, bear strong resemblance.

One painting, sold in the U.K. named the artist as Patrick Wybrant. The seller had seen enough of the paintings to say that the painting was "signed with the artist's usual signature 'Wybrant Artist.'"