Apple Mac mini SKU numbers difference
MGEM2**/A is the marketing number of the base model: Mac mini (Late 2014) 1.4GHz dual-core Intel Core i5/4GB. MGEM2GU/A is the number for the Greek?/former Commonwealth of Independent States (except Russia) market and MGEM2D/A is for the German market.

Some more country/market identifiers: LL = US/Canada, B = UK, BZ = Brazil, C = Canada, CH = China, E = most spanish countries (Mexico, Spain, Argentina), J = Japan, RU = Russia, X = Australia/New Zealand etc.