I looked up the serial numbers you listed for the singers.
AL 151977 is a 201, allotted in a group of 15000 on October 27, 1952.
AM 222852 is a 15, allotted in a group of 50000 on October 21, 1955.
It looks like you have a great group of machines there. I am glad you decided not to send them to the dump. I have found the older machines more reliable, easier to fix, and in general, great work horses when it comes to heavy duty sewing. When the computers give out in new machines, the old ones are still stitching right along!
I hope you find good homes for all of them. It looks like another charity (Quilts of Honor) might make good use of them.