Apple defines vintage products as those that have not been manufactured for more than five but less than seven years. Macs and other products on the vintage and obsolete list are generally no longer eligible for hardware service at a Genius Bar or Apple Authorized Service Providers.
That being said, also-obsolete Late 2012 model iMacs are currently eligible for Apple's pilot program that allows for repairs to continue into the vintage period, subject to parts availability. It's not clear if the Early 2013 model 21.5-inch iMac will also come under the pilot program, but Apple has expanded it to include additional Macs and other Apple devices in the past.
The Early 2013 21.5-inch iMac was originally only available to educational institutions, taking advantage of a cheaper dual-core Intel Core i3 processor and integrated graphics to offer pricing of $1099, which was $200 less than the entry-level pricing for the consumer 2.15-inch iMac models Apple was selling at the time. The education-only iMac, which carries a model number of ME699LL/A, also included just 4GB of RAM and a 500GB hard drive.