Apple Classifies Early 2013 21.5-inch iMac as Obsolete - MacRumors
Memory upgrade: Apple iMac 2012/2013/2014 (Howto)
How to Upgrade iMac Hard Drive or SSD 2012-2022: EveryMac.com
A-Tech 32GB Kit (4x8GB) RAM for Apple iMac (Late 2012, Late 2013, Late 2014, Mid 2015) | DDR3 1600MHz PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com
I got a FREE 2013 iMac 21.5 with internal upgrades including Samsung evo ssd and 16gigs of ram. Then used open legacy patcher to install Mac OS Venture 13.5 beta. : r/OSXBeta
iMac | 3.2 GHz Core i5 | 27 Inch | Late 2013 - Techable.com
2012 21.5-Inch Apple iMac Review: Slim, Sleek, And Stylish, But Far From Shallow | TechCrunch
Apple's new 'Assembled in USA' iMac a bear to upgrade, repair • The Register
Apple iMac 21.5" Late 2013 A1418 Intel Core i5 2.9GHz 1TB HDD 16GB RAM » eRecycler Online
2013 iMac teardowns reveal SSD slots, soldered-in CPU in the 21.5” model | Ars Technica