Seriously, this piece is bizarre. But I'm going to attempt to keep this to strict observations, at least at first.
Standard Disclaimer: This article is rife with opinions, as well as facts (which can mostly be verified through observation). My intent in writing it is to educate myself, and promote discussion--i.e., if you have other observations or research, please post in the comments at the bottom of the page.
Ok. The Met museum states this as being a 17th Century piece, and British. It was donated to the museum by one Mary Dykman Dean (wife of
Bashford Dean, who founded the Museum's Arms and Armour department). Other than the length at center back, that is all the information the museum has--I asked, and waited several weeks for them to get back with me before beginning to write this.