Click About this Mac. 3. Click More Info or click System Report in newer Macs. 4. In Hardware Overview look for Machine Identifier or Model Identifier in newer iMacs. 5. When you have the identifier (for example: iMac7,1), use it to find your model from our list on the left. iMac (iMac15,1) Core i5 3.3GHz 27 inch (Retina 5K)