In moving a friend's office, found a long-unused SCX-4100. Just to report, with the help of this thread, I did get it to scan under Mac OSX 10.12 (Sierra). On a machine running 10.8, in /Library/Image Capture/Devices, there exists "Samsung Scanner.app". It's only 1.8 MB, I copied it to the corresponding place in 10.12, then made the changes suggested above by MacTiger14. Also found a printer driver for it by searching the web (SCX-4200.zip). It now prints and scans fine!
Of course, as noted by Giuly, it might make more sense to buy a new Brother printer, for $100 - $150. I did have to buy new toner on ebay ($20), and remove ancient paper off the rollers of the old Samsung. But I saved money, and am recycling! Thanks to the original posters.