The unique thing about it is the pallet arbor birdge. It has no screws. It’s pinned on one side and just rests on the pin on the right. I can’t find a picture of it online. It has no stampings at all. It is in a cast iron case.
That center arbor design looks very familliar but I can’t place it. Did Sessions make an Open escapement?
[attachment=2:3k4sjf22]First Brocot Escapement.jpg[/attachment:3k4sjf22]