CluelessInSeattle you will find that the 820-XXXX number is imprinted (sometimes silk screened) on the board itself. See example attached.
Armed with that number you can then use your favorite online search engine to determine where this board belongs to etc. Here is an incomplete list that I use for my collection and repairs.
820-1881 A1150
820-1984 A1200 EMC 2111
820-2132 A1229 EMC 2137 MacBookPro3,1
820-2179 A1237 EMC 2142 MacBookAir 2008 1.8mhz
820-2223 A2210
820-2279 A1181
820-2375 A1304 EMC 2334 MacBookAir2,1
820-2496 A1181 Macbook 13
820-2523 A1286 MacBookPro mid2009
820-2530 A1278
820-2567 A1342 Macbook2009
820-2610 A1297
820-2784 A1311 EMC2389
820-2796 A1370 EMC2471 MacBookAir4.1
820-2838 A1369 MBA 2010
820-2850 A1286 MacBookPro mid 2010
820-2879 A1278 EMC 2351 MBPro7,1 with a "B" for 2010 mbp 13"
820-2901 A1312
820-2914 A1297 Late 2011
820-2915 A1286 EMC 2353
820-2915-B 2011 mbp 15" i7
820-2936 A1298 EMC 2419
820-2936-B 2011 mbp 13"
820-3023 A1369 MBA Core i5 1_7 13 _Mid-2011
820-3024 A1370
820-3208 A1465 EMC 2558 MacBookAir5,1
820-3209 A1466 EMC 2559 MacBookAir5,2
820-3332 A1398 EMC 2512