He said it was a 2015 all in one. Not sure about anymore specifics.
That's the exact machine I am on now! I use it all day, it's right next to my couch in the living room and use it as I watch TV and such. LOL
Model: iMac model# 17,1 - Retina 5k, 27-inch Late 2015
MacOS: Sonoma 14.8.4
Processor: 4GHZ Quad-Core Intel Core i7
Graphics: AMD Radeon R9 M395X 4GB
Memory: 16GB 1867 Max DDR3
Storage: 2TB Apple Hybrid Drive. (128GB is a SSD, the rest is a 7200RPM drive - acts as 1 drive) MacOS will automatically moves your most used programs onto the 128GB SSD portion of the drive speeding things up.. Remember, back in 2015 SSD's were serious $$$$ so they made Hybrid drives.
This is a VERY capable machine!! Maybe NOT the fastest, if you are running something from the spindle side of the drive, but you can still run ALL current Mac Apps even the newest versions of all of the Adobe Creative Suite programs, MS Office, Pro Tools etc etc!! Maybe not Call of Duty - LOL
My other 27" iMac is a late 2017 that has 48GB ram, 1TB external Thunderbolt 3 NVME m.2 SSD, 2TB Apple Hybrid Drive and kick as video card. Starting in 2017, and the introduction of the Thunderbolt 3 port, you could boot and run from a MUCH faster drive in modern times then the built in Hybrid drives. That is my power house system and I only turn that on when I need some serious power, like mixing 100 audio tracks in Pro Tools or Adobe shit, etc. I want it to last a long time. Both machines are running macOS Sonoma, even though Apple stop supporting them years ago with MacOS.
You can get old iMac's on eBay for not a lot. Knowing you can use OCLP is a game changer! Remember, you can runs Windows on these machines and Linux as well natively booting to the OS using BOOTCAMP. Can't run Win 11 unless you use a VM Program like Parallels. Win 11 runs great in Parallels on my 2017 iMac with all the ram I have and the external SSD. Boots up like in 15 secs or so.
Tell him that 2015 is complete shit and you'll take it off his hands - LOL!