Cushman's Bakery appears to have actually begun in New York City, but Mr.Cushman moved his bakery to Portland, Maine and later expanded to include a Lynn, Massachusetts operation.
The bakery closed in 1964, and rights to the recipes may have gone to Oakhurst Dairy in Maine. I have never heard from a former Cushman's baker, and I have never heard anything about a recipe book.
My mostly unsuccessful efforts are here:
Cushman's Bakery Scotch Cookies