661-03279 Apple Logic Board 3.1GHz Intel Core i5 Quad Core 16GB HDD for iMac 21.5" Retina 4K Late 2015
Probably of no use to anyone here, but the 2.8GHz late 2015 iMac logic board requires a different heatsink than the 1.6GHz board because the CPU is in a different location. Ask
21.5" Late 2013 Apple iMac A1418 - Logic Board 2.9Ghz i5 - ME087LL/A - 661-7503 - TEKDEP.com Parts Tools Gadgets Repair
Original A1419 Motherboard 820-4652-A For Apple iMac Retina 5K 27-inch Logic Board 661-00193 Late 2014 Mid 2015 EMC 2806 - AliExpress
27 inchLate 2013 Apple iMac A1419 - Logic Board 3.4Ghz i5 2GB- ME089LL/A, 661-7517 - TEKDEP.com Parts Tools Gadgets Repair
iMac 27" Logic Board, 3.3GHz, i5, 2GB VRAM, Late 2014 / Mid 2015 DIY Parts replacement Logic Boards