I found this cool old pancake style padlock at a 1900 permission home...from what I've seen looks like it dates to mid to late 1800's. Been awesome if I'd found the key.
What really helped me in picking my 1800's lock was to find a picture from an old catalog. I contacted a lock museum, and they sent me the image. The image shows you what your key should look like.
"...The former Eagle Lock Co. of Terryville, CT was formed in 1854 - went out-of-business in June, 1975 - Lori Corp. of Southington, CT purchased some of the machinery at auction and continued to make a few of the old Eagle products even after they were acquired by Kaba Ilco Corp. in 1978..."