A little (alot) research reveals new information every day it seems.
As Woody mentioned above, there is an outstandingly detailed history of the company on
oldtoolheaven.com. This source notes the company's beginnings in 1861.
However, I've been doing a bit of research and have thus far found the following, noting the founders are Gunn and Charles H. Amidon:
Items of interest:
1. 1860 U.S. Census: Levi J. Gunn is listed as a "Manufacturer of Carpenter's Tools." In the 1855 census, they are mostly there as well but all list their occupations as "Artisan." Even more interesting, several of his immediate neighbors, as their occupation, list "Carpenter's Tools." I am ASSUMING they are neighbors as they are ordered in the "order of visitation" by the census taker. Levi is #410. For reference, they are:
#411 - Chauncey Bryant - "Manufacturer of Carpenter's Tools"
#412 - Edward W. Hubbard - "Carpenter's Tools"
#415 - William Amidon - "Carpenter's Tools"
#415 - Harrison Amidon - "Carpenter's Tools"
#415 - Nelson Brackett - "Carpenter's Tools"
#415 - Elijah Brown - "Carpenter's Tools"
#415 - George Colesworthy - "Carpenter's Tools"
#416 - Hopkins Woods - "Treasurer of Tool Co."
#417 - Charles H. Amidon - "Manufacturer of Carpenter's Tools"
#418 - Luther Allis - "Plane Maker"
#422 - Dwight Haynes - "Plane Maker"
2. In the 1865 Census, I believe Mr. Gunn lists his occupation as "Mechanic" - It's difficult to read.
3. 1870 Census, Mr. Gunn is listed as a "Manufacturer"
4. 1865 William Amidon (and most of his male family members) is listed as a carpenter.
5. Can't find much on Charles H. Amidon. In the 1865 census, he too (along with most all around him) is listed as "Mechanic" (I think, tough to read) // 1870 Census he is listed as "Manuf"
6. Hartford Courant - 3/19/1862 advert announcing "Amidon's Wringer" manufactured by Gunn, Amidon & Holland.
7. "History of Greenfield, Shire Town of Franklin County, Massachusetts" notes that Gunn, Amidon & Holland built shops on Cherry Rum Brook in September of 1861.