I was wondering if anyone knows this makers mark, I believe it is an American made case, perhaps 1850's.

Searching the web I have seen where it is identified as both Mathey and Brother or Middleton & Brother, I think the symbol below their initials is the eagle or bird silver mark.

Tom,
Niebling's book lists, Mathey Bros. (L.& A.), 1860 to 1880, cases marked "M & B"; see Jacot & Courvoisier-New York City. Under Jacot (E) & Courvoisier (G), 1839 to 1849, then name changed to Jacot (E.), Courvoisier (G.) & Co. Louis Mathey was the "Co."; this until 1856. Louis Mathey retired and Mr.Jacot left and for one year, until 1857, company name was Courvoisier (G.) & Mathey (Louis, Jr.). Louis, Jr., replaced his retired father. Then George Courvoisier died, and his son, Ulysses, replaced him until 1860-no company name change. Ulysses left the company in 1860, August Mathey, a brother, joined the company and the name changed to (L.&A.) Mathey Bros. They sold out in the year 1880 to still another Courvoisier (George) & (George) Wilcox. All in New York City.

Hope this helps a little.
Brian C.

Tom

I foud one mark on a ~1870 Howard watch case (picture below). The Howard marks are very likely "Middleton & Brother". Note the differences - without dots and the right side of the rectangle rounded. Unless they changed their mark yours might be the other one.

Gerald