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Here is a list of model number in different countries. According to the list, your iphone is from Apple US.

Germany - T-Mobile
MC603DN/A – 16GB Black
MC605DN/A – 32GB Black

Japan - Softbank
MC603J/A - 16GB Black
MC605J/A - 32GB Black

Spain - Movistar, Orange, Vodafone
MC603Y/A – 16GB Black
MC605Y/A – 32GB Black

United States - AT&T
MC608LL/A - 16GB Black
MC610LL/A - 32GB Black
Apple
MC318LL/A - 16GB Black
MC319LL/A - 32GB Black

Australia
MC603X/A - 16GB Black
MC605X/A - 32GB Black

Canada
MC603C/A - 16GB Black
MC605C/A - 32GB Black

France
MC603FB/A - 16GB Black
MC605FB/A - 32GB Black

Hong Kong
MC605ZP/A - 32GB Black
MC603ZP/A - 16GB Black

Italy
MC603IP/A - 16GB Black
MC605IP/A - 32GB Black

New Zealand
MC603X/A - 16GB Black
MC605X/A - 32GB Black

Singapore
MC603ZA/A - 16GB Black
MC605ZA/A - 32GB Black

Sweden
MC603KS/A – 16GB Black
MC605KS/A – 32GB Black

United Kingdom
MC603B/A - 16GB Black
MC605B/A - 32GB Black