Hi,
Joe brought to my attention this Sears Iowa by Davis which I had never seen an example of:
http://www.shopgoodwill.com/auctions...-20873619.html
According to the Ismacs Sears article the "Iowa" was made by American and was a round bobbin Vibrating shuttle model with no mention of this Davis version.
The Iowa is a Davis model H and was made c. 1900.
Jon