@garegin like @livfe already mentioned, the easiest way to identify your specs would be by using your computers serial number. It will give you the memory as well as the storage information.
The only other way would be by looking at the memory IC's itself. Each one of the 8GB and 16GB configuration uses 3 different IC's, which leaves you with a total of 6 possibilities. Commonly used IC's are HYNIX, Micron, or Samsung. Apple, in it's habitual paranoid way, may have had those IC's marked with their own part numbers:
333S00125
333S00068
333S00166
333S00126
333S00070
333S00167
those are all LDDR3-2133 BGA178 IC's but are different and not just in capacity.
[image|3387753]
As for your "SSD" storage, again, you are dealing with NAND IC's Apple commonly uses Toshiba IC's for these (may or may not be marked in the APPLE Way :-) Here are the numbers for those
[image|3387758]
and here are the locations
[image|3387764]
The boards with a higher storage capacity do have additional solder points. I do hope that this will help you out. Of course, you could also just post a couple of good pictures of your logic board (both sides and IC covering removed) so we could help you further with this.
[guide|21499]